HomeMy WebLinkAboutSDP 15-22; QUARRY CREEK PA R-2; GEOTECHNICAL REPORT; 2015-07-22DUE DILIGENCE
GEOTECHNICAL REPORT
QUARRY CREEK -LOT 2
CARLSBAD, CALIFORNIA
PREPARED FOR
LENNAR
ALISO VIEJO, CALIFORNIA
JULY 22, 2015
PROJECT NO. 07135-42-07
,
GEOCON
INCORPORATED
GEOTECHNIC Al ■ ENVIRONMENTAL ■ MATERIAL< 0
Project No. 07135-42-07
July 22, 2015
Lennar
95 Enterprise, Suite 200
Aliso Viejo, California 92656
Attention: Mr. John Colletti
Subject: DUE DILIGENCE GEOTECHNICAL REPORT
QUARRY CREEK -LOT 2
CARLSBAD, CALIFORNIA
Dear Mr. Colletti:
In accordance with your authorization, we are pleased to submit our due diligence geotechnical
report for Lot 2 area within the Quarry Creek project. Conclusions and recommendations presented
herein are based on review of available published geotechnical reports and literature, observations
during previous grading performed on the property for reclamation, previous subsurface geotechnical
exploration and site reconnaissance of existing conditions.
The accompanying report presents findings from our studies relative to geotechnical engineering
aspects of developing the property. The site is considered suitable for the proposed improvements
provided the recommendations of this report are followed.
Should you have questions regarding this report, or if we may be of further service, please contact
the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
CEG 1778
AS:RCM:dmc
(3) Addressee
1?-~fM;~
GE~~
6960 Flanders Drive ■ San Diego, California 92121-297.4 ■ Telephone 851.551.6900 ■ fax 858.558.6159
TABLE OF CONTENTS
1. PURPOSE AND SCOPE ...................................................................................................................... 1
2. PREVIOUS SITE USAGE AND GRADING ....................................................................................... 1
3. SITE AND PROJECT DESCRIPTION ................................................................................................ 2
4. SOIL AND GEOLOGIC CONDITIONS .............................................................................................. 3
4.1 Compacted Fill (Qcf) .................................................................................................................. 3
4.2 Undocumented Fill (Qudf) ......................................................................................................... 3
4.3 Previously Placed Fill (Qpf) ....................................................................................................... 4
4.4 Alluvium (Qal) ........................................................................................................................... 4
4.5 Terrace Deposits (Qt) ................................................................................................................. 4
4.6 Santiago Formation (Ts) ............................................................................................................. 5
5. GROUNDWATER ............................................................................................................................... 5
6. GEOLOGIC HAZARDS ....................................................................................................................... 5
6.1 Faulting and Seismicity .............................................................................................................. 5
6.2 Liquefaction ................................................................................................................................ 7
6.3 Landslides ................................................................................................................................... 8
7. CONCLUSIONS AND RECOMMENDATIONS ................................................................................ 9
7.1 General ....................................................................................................................................... 9
7.2 Excavation and Soil Characteristics ........................................................................................... 9
7 .3 Preliminary Grading Recommendations ................................................................................... 10
7.4 Slope Stability .......................................................................................................................... 12
7.5 Seismic Design Criteria ............................................................................................................ 13
7.6 Preliminary Foundation Recommendations ............................................................................. 15
7. 7 Preliminary Retaining Wall Recommendations ....................................................................... 20
7 .8 Detention Basin and Bioswale Recommendations ................................................................... 22
7.9 Site Drainage and Moisture Protection .................................................................................... 23
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map
Figure 3, Geologic Cross Section
Figures 4 -6, Slope Stability Analysis
Figure 7, Typical Retaining Wall Drain Detail
APPENDIX A
RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
DUE DILIGENCE GEOTECHNICAL REPORT
1. PURPOSE AND SCOPE
This report presents the results of a due diligence geotechnical report for Lot 2 in the Quarry Creek
development. The purpose of this report is to provide preliminary information with respect to surface
and subsurface soil conditions and general site geology, and to identify geotechnical constraints that
may impact development of the property. In addition, we are providing preliminary grading
recommendations, foundation design criteria, concrete flatwork recommendations, a:nd retaining wall
recommendations that can be utilized in developing project budgets. The scope of this investigation
also included a review of readily available published and unpublished geologic literature, aerial
photographs and the following documents previously prepared for the property:
1. Update Geotechnical Investigation, Quarry Creek, Carlsbad/Oceanside, California,
prepared by Geocon Incorporated, dated February 24, 2015 (Project No. 07135-42-05).
2. Final Report of Testing and Observation Services During Site Grading, Quarry Creek,
Carlsbad, California, prepared by Geocon Incorporated, dated April 4, 2013 (Project
No. 07135-42-02).
3. Mass Grading Plans for Quarry Creek, prepared by Project Design Consultants, City of
Carlsbad approval June 4, 2015.
4. Exhibit for Quarry Creek, Planning Area "R-1" and "R-2 ", prepared by SB&O, plot date
July 15, 2015.
The site is located south of State Route 78 and west of College Boulevard in Carlsbad, California
(see Vicinity Map, Figure 1).
Lot 2 has been partially graded as part of the reclamation process for the former aggregate mining
plant the previously occupied the property. Geocon Incorporated performed compaction testing and
observation services during reclamation grading. Reference 2 is the as-graded report prepared for
reclamation grading. As-graded conditions are shown on the Geologic Map (Figure 2). The base map
used to plot geology was a CAD file of Reference 4 provided by SB&O.
Other reports reviewed as part of this study are summarized on the List of References at the end of
this report.
2. PREVIOUS SITE USAGE AND GRADING
The Quarry Creek property has undergone many years of mining, crushing, and screening to produce
commercial aggregate products. The majority of previous mining activity occurred in the eastern and
southern portions of the overall Quarry Creek property. Mining waste products were placed in
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canyon or pit areas to reclaim quarry excavations. This resulted in placement of mostly
undocumented fill in depressions, as well as some compacted fill. A former concrete batch plant and
base-coarse crushing and screening plant operated by Hanson Aggregates occupied the property.
Other portions of the property were previously used for storage purposes, which include stockpiles of
concrete and asphalt rubble, soil stockpiles, and other materials.
Reclamation grading of the previously mined area commenced in July 2011 and was completed in
December 2012. During reclamation grading, undocumented fills were removed and replaced as
compacted fill. Alluvium and undocumented fill was removed to approximately 3 feet above
groundwater elevation and replaced with compacted fill. Drop structures, levees, and rock revetment
slopes were constructed along and in Buena Vista Creek drainage south of the project site.
3. SITE AND PROJECT DESCRIPTION
The original valley-slope topography has been lowered by quarry operations and then regarded to the
current sheet grade elevations during reclamation grading. The northern portion of the lot is in an
ungraded condition.
The site is underlain by compacted fill placed during reclamation grading, undocumented fill and
alluvium within the southern half of the lot, native Terrace Deposits at the northeast comer, and
Santiago Formation along the north side of the property. Reclamation grading has resulted in 2: 1 or
flatter cut and fill slopes with heights up to approximately 30 to 40 feet along the north and south
sides of the property. The site currently slopes from northeast to southwest with site elevations
varying from a high of approximately 155 feet Mean Sea Level (MSL) to 104 feet MSL near the
southwest comer.
Currently, regrading of the Quarry Creek property is occurring. Based on the grading plans
(Reference 3), regrading on Lot 2 will result in approximately 3 to 5 feet of fill being placed above
current sheet grade elevations and cuts up to approximately 35 feet along the northern property limit
adjacent to Haymar Drive. A 5-foot-high surcharge fill will be placed above planned sheet grade
elevations on the portion of Lot 2 where groundwater prevented complete removal of undocumented fill
and alluvium during previous reclamation grading. Settlement monitoring of the surcharge fill will be
performed under the current grading operation. Once settlement monitoring indicates settlement as a
result of the surcharge fill is complete, the surcharge fill will be removed and the pad will be left in the
sheet graded condition shown on the referenced grading plans with sheet grade pad elevations ranging
from approximately 119 feet MSL at the northeast comer to 109 feet MSL at the southwest comer.
Final plans for development have not yet been prepared. However, we understand plans are to
construct 3-to 4-story multi-family buildings. We expect fine grading will consist of cuts and fills of
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less than 3 feet to construct building pads. An update geotechnical report should be prepared once
development plans are ready.
The site description and proposed development are based on a site reconnaissance, review of
previous reports and plans, and our understanding of proposed development. If development plans
differ significantly from those described herein, we should be contacted for review and possible
revisions to this report.
4. SOIL AND GEOLOGIC CONDITIONS
Four surficial soil deposits and two geologic formations are currently present on the property or in
adjacent areas. Surficial soil deposits include undocumented fill, compacted fill, previously placed
fill, and alluvium. Formational units include: Quaternary-age Terrace Deposits and Tertiary-age
Santiago Formation. Mapped limits of the current geologic units are shown on the Geologic Maps
(Figure 2). A geologic cross section is presented on Figure 3. The surficial soil types and geologic
units are described below.
4.1 Compacted Fill (Qcf)
Up to approximately 25 feet of compacted fill was placed across the lot during reclamation grading.
The deepest area of fill is near the top of the southern slope. Observation and compaction testing of
the fill has been performed by Geocon Incorporated. A report documenting compaction tests and as-
graded conditions was prepared in 2013 (see Reference 2). The fill is predominately comprised of
silty to clayey sand with varying amounts of rock fragments, soil rock fills, and windrows of oversize
rock and concrete. A 10-foot hold-down for oversize rock was provided during reclamation grading.
Compacted fill is considered suitable for support of additional fill and structural loads.
4.2 Undocumented Fill (Qudf)
Undocumented fill exists in the northeast portion of the lot beyond the previous reclamation grading
limit and within the slope area and existing access road from Haymar Drive. The majority of this
undocumented fill will likely be removed to achieve sheet grades under the current grading operation
based on proposed cuts shown on Reference 3. Undocumented fill is unsuitable in its present
condition, and will require removal and recompaction to support additional fill or structural
improvements if encountered on the property.
In the southern half of Lot 2, a limited amount of undocumented fill was left in-place during
reclamation grading due to the presence of groundwater. Based on our observations during
reclamation grading and potholes performed, we expect less than 3 to 5 feet of fill was left below
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groundwater in some areas. We do not expect the presence of the undocumented fill will impact
future development. This area will also be surcharged during the current grading operation to further
consolidate the undocumented fill.
4.3 Previously Placed Fill (Qpf}
Previously placed fill exists within and near Haymar Drive near the northwest and northeast comers
of the property. The approximate limit of the previously placed fill is shown on Figure 2 (Geologic
Map). These soils are outside of Lot 2 and should not impact the project.
4.4 Alluvium (Qal)
Alluvial deposits are present within the southern half of Lot 2. Based on observations during
previous grading, the alluvial soils generally consist of loose, porous dark gray to dark brown, very
clayey, fine to medium sand, and clayey sand and silt with occasional layers of slightly silty sand.
The alluvium is buried and should not impact the project. Settlement monitoring was performed after
the completion of reclamation grading to measure consolidation of the alluvium as a result of fill
placed during reclamation grading. The results of the settlement monitoring are presented in
Reference 2 and indicate settlement of the alluvium as a result of the previous fill placement was
complete.
Recently, survey shots were performed on the settlement monument installed during reclamation
grading. The survey data indicates essentially no settlement has occurred since the last reading in
December 2012.
Current grading will result in the placement of an additional surcharge fill over the alluvium to
induce consolidation settlement. Settlement monitoring will be performed once the surcharge fill is
placed. The surcharge fill will remain on the lot until survey data indicates settlement as a result of
the surcharge fill is essentially complete. It is our opinion that the presence of the alluvium will not
impact the proposed project.
4.5 Terrace Deposits (Qt)
River terrace deposits consisting of medium-dense to dense, light reddish-brown to olive-brown,
gravelly, silty to clayey, medium to coarse sand to cohesionless sand with occasional layers of silty
clay are present in the western portion of the site. Except near depositional contacts ( or
unconformities) with older formations, this unit is typically massive to horizontally bedded,
relatively dense and exhibits low compressibility characteristics. The sandy zones are suitable for
support of fill and/ or structural loads in their present condition. The clayey zones, however, possess
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low shear strength and high expansion potential. The Terrace Deposits are suitable for support of the
planned improvements.
4.6 Santiago Formation (Ts)
The Eocene-aged Santiago Formation, consisting of dense, massive bedded light brown to greenish-
gray sandstones and thin interbedded siltstones is present along the north and west sides of the lot.
The Santiago Formation is generally granular and possesses suitable geotechnical characteristics in
either an undisturbed and/or properly compacted condition. However, the occurrence of clayey
siltstones and claystone layers in this unit may generate moderate to highly expansive materials, or
localized expansive zones at grade. Where practical, clayey zones of the Santiago Formation should
be placed at least 3 feet below proposed subgrade elevations.
5. GROUNDWATER
Groundwater was encountered during previous grading between elevation 70 to 80 feet MSL. Depth
of groundwater is subject to fluctuation from natural seasonal variations. Based on our understanding
of the proposed project, groundwater should not impact development of Lot 2.
6. GEOLOGIC HAZARDS
6.1 Faulting and Seismicity
Review of geologic literature, previous geotechnical reports for the property, and observations during
our current field investigation indicates no active faults traverse the property. One fault was observed
in Salto Intrusive rock across the quarry slope in the northeast comer of the Quarry Creek property.
However, an exploratory trench excavated through the Tertiary Santiago Formation across the fault
confirmed the fault did not displace the Eocene-age sedimentary unit. As such, the fault is considered
inactive and not a constraint to the property.
According to the results of the computer program EZ-FRISK (Version 7.62), 8 known active faults
are located within a search radius of 50 miles from the property. The nearest known active fault is
the Newport-Inglewood-Rose Canyon Fault Zone, located approximately 6 miles east of the site and
is the dominant source of potential ground motion. Earthquakes that might occur on the Newport-
Inglewood-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. The estimated
deterministic maximum earthquake magnitude and peak ground acceleration for the Newport
Inglewood -Rose Canyon Fault are 7 .5 and 0.34 g, respectively.
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We used Boore-Atkinson (2008) NGA USGS2008, Campbell-Bozorgnia (2008) NGA USGS 2008,
and Chiou-Youngs (2008) NGA acceleration-attenuation relationships in the calculation of the peak
ground accelerations (PGA). Table 6.1.1 lists the estimated maximum earthquake magnitudes and
PGA's for the most dominant faults for the site location calculated for Site Class D as defined by
Table 1613A.5.3 of the 2010 CBC.
TABLE 6.1.1
DETERMINISTIC SPECTRA SITE PARAMETERS
Maximum Peak Ground Acceleration
Distance Earthquake Fault Name from Site Boore-Campbell-Chiou-
(miles) Magnitude Atkinson Bozorgnia Youngs (Mw) 2008 (g) 2008 (g) 2008 (g)
Newport-Inglewood-Rose Canyon 6 7.50 0.30 0.26 0.34
Elsinore 21 7.85 0.21 0.15 0.19
Coronado Bank 23 7.40 0.18 0.12 0.14
Palos Verdes Connected 23 7.70 0.19 0.13 0.16
San Joaquin Hills Thrust 35 7.10 0.18 0.10 0.09
Earthquake Valley 42 6.80 0.13 0.09 0.11
San Jacinto 45 7.88 0.13 0.08 0.10
Chino 47 6.80 0.08 0.05 0.05
We used the computer program EZ-FRISK to perform a probabilistic seismic hazard analysis. The
computer program EZ-FRISK operates under the assumption that the occurrence rate of earthquakes
on each mapped Quaternary fault is proportional to the fault slip rate. The program accounts for
earthquake magnitude as a function of fault rupture length. Site acceleration estimates are made
using the earthquake magnitude and distance from the site to the rupture zone. The program also
accounts for uncertainty in each of following: ( 1) earthquake magnitude, (2) rupture length for a
given magnitude, (3) location of the rupture zone, (4) maximum possible magnitude of a given
earthquake, and (5) acceleration at the site from a given earthquake along each fault. By calculating
the expected accelerations from considered earthquake sources, the program calculates the total
average annual expected number of occurrences of site acceleration greater than a specified value.
We utilized acceleration-attenuation relationships suggested by Boore-Atkinson (2008) NGA
USGS2008, Campbell-Bozorgnia (2008) NGA USGS 2008, and Chiou-Youngs (2008) in the
analysis. Table 6.1.2 presents the site-specific probabilistic seismic hazard parameters including
acceleration-attenuation relationships and the probability of exceedence for Site Class D.
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TABLE 6.1.2
PROBABILISTIC SEISMIC HAZARD PARAMETERS
Peak Ground Acceleration
Probability of Exceedence Boore-Atkinson, Campbell-Bozorgnia, Chiou-Youngs,
2008 (g) 2008 (g) 2008 (g)
2% in a 50 Year Period 0.52 0.42 0.47
5% in a 50 Year Period 0.39 0.32 0.35
10% in a 50 Year Period 0.31 0.25 0.27
The California Geologic Survey (CGS) provides a computer program that calculates the ground
motion for a 10 percent of probability of exceedence in 50 years based on the average value of
several attenuation relationships. Table 6.1.3 presents the calculated results from the Probabilistic
Seismic Hazards Mapping Ground Motion Page from the CGS website.
TABLE 6.1.3
PROBABILISTIC SITE PARAMETERS FOR SELECTED FAUL TS
CALIFORNIA GEOLOGIC SURVEY
Calculated Acceleration (g) Calculated Acceleration (g) Calculated Acceleration (g)
Firm Rock Soft Rock Alluvium
0.27 0.29 0.33
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. Seismic design of the structures should be
evaluated in accordance with the California Building Code (CBC) guidelines.
6.2 Liquefaction
Liquefaction analyses were performed for previous geotechnical investigations for the reclamation
grading. Results of the analyses indicate alluvial deposits below the groundwater should not liquefy
for the design level acceleration. However, design accelerations for under current building codes
have significantly increased over the last several years. Under current design accelerations, portions
of the alluvium below groundwater could experience liquefaction. Liquefaction, should it occur, is
expected to be limited to the area within the existing Buena Vista Creek drainage, and in the
tributary drainage southwest of the site. With respect to the alluvium left in place within Lot 2, the
alluvium is expected to be less than 10 feet thick, has been surcharged with approximately 15 to
20 feet of fill, will receive an additional 5 feet of fill to achieve proposed sheet grades, and will be
Project No. 07135-42-07 -7 -July 22, 2015
surcharged with an additional 5 feet of fill during the current grading operation. In our opinion,
liquefaction, if it were to occur in this area would not cause surface manifestations (i.e., sand boils).
Settlement, should it occur is expected to be relatively uniform and less than I-inch total. We
estimate differential settlement as a result of liquefaction to be ½-inch or less.
6.3 Landslides
Based on a review of aerial photographs, topographic maps, and available literature, no landslides
exist at the site or adjacent areas that could impact the property.
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7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7 .1.1 From a geotechnical engineering standpoint, it is our opinion that the site is suitable for the
development of 3-to 4-story multifamily structures provided the recommendations
presented herein are implemented in design and construction of the project.
7.1.2 The site is underlain by compacted fill, undocumented fill, alluvium, Terrace Deposits, and
Santiago Formation. With the exception of the undocumented fill buried in the southern
half of the lot, we expect current grading will result in the removal of undocumented fill.
The undocumented fill and alluvium within the southern portion of the lot that was left in-
place due to groundwater will be surcharged during the current grading, will be overlain by
25 to 30 feet of compacted fill at the completion of the current grading, and should not
impact proposed development. The Terrace Deposits and Santiago Formation are expected
to be suitable for support of planned improvements.
7.1.3 The property is approximately 7 miles from the Newport Inglewood/Rose Canyon Fault. It
is our opinion active and potentially active faults do not extend across or trend toward the
site. Risks associated with seismic activity consist of the potential for strong seismic
shaking. Building setbacks will not be required for the planned development due to
faulting.
7.1.4 Subsurface conditions observed may be extrapolated to reflect general soil/geologic
conditions; however, some variations in subsurface conditions should be anticipated.
7.1.5 An update geotechnical report should be performed once development plans have been
prepared to reflect as-graded conditions that will exist at the completion of the current
grading and to provide recommendations based on planned construction.
7.2 Excavation and Soil Characteristics
7.2.1 Excavation of the Terrace Deposits and Santiago Formation is expected to require a heavy
to very heavy effort to excavate. Excavation of compacted fill is expected to require a
heavy effort using conventional grading equipment.
7 .2.2 The soil encountered in the field investigation is considered to be "expansive" ( expansion
index greater than 20) as defined by 2013 California Building Code (CBC)
Section 1803.5.3. Table 7.2 presents soil classifications based on the expansion index.
Based on the results of laboratory testing performed during previous geotechnical
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investigations and grading for the Quarry Creek property, we expect the on-site materials
will possess a "very low" to "very high" expansion potential (Expansion Index of 20 and
greater).
TABLE 7.2
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
ASTM 4829 AND 2013 CBC
Expansion Index (EI) Expansion Classification 2013 CBC
ASTM4829 Expansion Classification
0-20 Very Low Non-Expansive
21-50 Low
51-90 Medium
91 -130 High Expansive
Greater Than 130 Very High
7.2.3 We performed laboratory tests on samples of the site materials during previous
geotechnical investigations and grading to evaluate the percentage of water-soluble sulfate
content. Results from the laboratory water-soluble sulfate content tests indicate that the on-
site soils at the locations tested possess "negligible" sulfate exposure to concrete structures
as defined by 2013 CBC Section 1904 and ACI 318-08 Sections 4.2 and 4.3. We
recommend the requirements set forth by 2013 CBC Section 1904 and ACI 318 be
followed when determining the type of concrete to be used. 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 may be needed if improvements that could be
susceptible to corrosion are planned.
7.3 Preliminary Grading Recommendations
7 .3 .1 The following preliminary grading recommendations are based on expected soil conditions
on the lot at the completion of the current grading operation. Modification to these
recommendations may be needed and can be provided in update reports once finalized
development plans are prepared and actual soil conditions at the completion of the current
grading operation are known.
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7.3.2 All grading should be performed in accordance with the Recommended Grading
Specifications contained in Appendix A. Where the recommendations of Appendix A
conflict with this section of the report, the recommendations of this section take
precedence.
7.3.3 Prior to commencing grading, a preconstruction conference should be held at the site with
the owner or developer, grading contractor, civil engineer, and geotechnical engineer in
attendance. Special soil handling and/or the grading plans can be discussed at that time.
7.3.4 Grading should be performed in conjunction with the observation and compaction testing
services of Geocon Incorporated. Fill soil should be observed on a full-time basis during
placement and tested to assess in-place dry density and moisture content.
7.3.5 Site preparation should begin with removal of all deleterious material and vegetation. The
depth of removal should be such that material exposed in cut areas or soil to be used for
fill is relatively free of organic matter. Deleterious material generated during stripping
and/or site demolition should be exported from the site.
7.3.6 After removal of unsuitable material as recommended above, the existing ground surface
(including previous compacted fill soil) to receive additional fill should be scarified
approximately 12 inches, moisture conditioned, and compacted.
7.3.7 The site should then be brought to final subgrade elevations with structural fill compacted
in layers. In general, soils native to the site 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. All fill, backfill, and scarified ground
surfaces should be compacted to a dry density of at least 90 percent of maximum dry
density near to slightly above optimum moisture content, as determined in accordance with
ASTM Test Procedure D 1557. Fill areas with in-place density test results indicating
moisture contents less than optimum will require additional moisture conditioning prior to
placing additional fill.
7.3.8 To reduce the potential for differential settlement, it is recommended that the cut portion
of building pads with cut-fill transitions be undercut at least 3 feet and replaced, where
practical, with "very low" to "medium" expansive compacted fill soils.
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7.3.9 Cut pads exposing concretions, cemented material, or expansive soil should be undercut at
least 3 feet and replaced with properly compacted "very low" to "medium" expansive soil
to facilitate excavation of foundations and shallow utilities.
7.3.10
7.3.11
7.3.12
7.3.13
7.3.14
Undercuts (overexcavations) performed on pads with cut-fill transitions, cemented
sandstone, hard rock or expansive soil materials at grade should be undercut at a gradient
of 1 percent toward the street or toward the deepest fill area to provide drainage for
moisture migration along the contact between the native soil and compacted fill.
Regrading should be performed such that highly expansive soils, if encountered, are placed
in the deeper fill areas and outside of building pads and slope zones. Materials within
3 feet of finish grade on lots and the upper 12 inches of subgrade within streets, where
practical, should consist of very low to medium expansive soils (soil with an Expansion
Index less than 90).
Cut and fill slopes should be constructed at an inclination of 2: 1 (horizontal to vertical) or
flatter. An approximately 35-foot-high 1.5: 1 cut slope in the Santiago Formation will be
constructed during the current grading along the north property limits. This 1.5: 1 slope is
acceptable provided it is free of adverse bedding. The slope excavation will be observed
during grading by a representative of Geocon Incorporated to check that soil and geologic
conditions do not differ significantly from those anticipated and adverse bedding does not
exist.
All fill slopes should be constructed of granular material and compacted out to the face of
the finish slope.
Excavations in cemented zones of formational units will likely generate oversize rock
chunks. Oversized materials can be placed in fill areas in accordance with the
recommendations contained within the Recommended Grading Specifications in
Appendix A. Oversize materials (rocks or hard lumps in excess of 12 inches in least
dimension) should be kept at least 10 feet below proposed finish grade within building
pads and at least 2 feet below the deepest utility within street right-of-ways. Modifications
to the hold down depths can be made at the owner's desecration.
7.4 Slope Stability
7.4.1 Slope stability analyses, utilizing average drained direct shear strength parameters, indicate
proposed fill slopes constructed with on-site granular materials and cut slopes within
formational material should have calculated factors of safety of at least 1.5 under static
Project No. 07135-42-07 -12 -July 22, 2015
conditions with respect to both deep-seated failure and shallow sloughing conditions.
Results of the analyses are presented on Figures 4 through 6. Additionally, an inclination
of 1.5 to 1 (horizontal to vertical) is acceptable for slopes excavated into the Santiago
Formation provided no adverse jointing, fractures, or bedding exist. All cut slopes should
be observed by a geologist to assess if adverse bedding, jointing, or fractures exist.
7.4.2 The outer 15 feet ( or a distance equal to the height of the slope, whichever is less) of fill
slopes should be composed of properly compacted granular "soil" fill to reduce the
potential for surficial sloughing.
7.4.3 Fill slopes should be overbuilt at least 3 feet and cut back to the design finish grades.
Alternatively, fill slopes can be compacted by backrolling with a loaded sheepsfoot roller
or tracked walked by sufficiently by a D-8 dozer or equivalent, at vertical intervals not to
exceed 4 feet. Slope should be uniformly compacted to a dry density of at least 90 percent
of the laboratory maximum dry density to the face of the finished slope.
7.4.4 All 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. Slope planting should generally consist of
drought tolerant plants having a variable root depth. Slope watering should be kept to a
minimum to just support the plant growth.
7 .5 Seismic Design Criteria
7.5.1 We used the computer program U.S. Seismic Design Maps, provided by the USGS.
Table 7.5.1 summarizes site-specific design criteria obtained from the 2013 California
Building Code (CBC; Based on the 2012 International Building Code [IBC] and ASCE 7-
10), Chapter 16 Structural Design, Section 1613 Earthquake Loads. The short spectral
response uses a period of 0.2 second. The building structures and improvements should be
designed using a Site Class D. We evaluated the Site Class based on the discussion in
Section 1613.3.2 of the 2013 CBC and Table 20.3-1 of ASCE 7-10. The values presented
in Table 7.5.1 are for the risk-targeted maximum considered earthquake (MCER)-
Project No. 07135-42-07 -13 -July 22, 2015
TABLE 7.5.1
2013 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2013 CBC Reference
Site Class D Section 1613.3.2
MCER Ground Motion Spectral Response 1.068g Figure 1613.3.1(1) Acceleration -Class B (short), Ss
MCER Ground Motion Spectral Response 0.413g Figure 1613.3.1(2) Acceleration-Class B (1 sec), S1
Site Coefficient, FA 1.073 Table 1613.3.3(1)
Site Coefficient, Fv 1.587 Table 1613.3.3(2)
Site Class Modified MCER 1.145g Section 1613.3.3 (Eqn 16-37) Spectral Response Acceleration (short), SMs
Site Class Modified MCER 0.656g Section 1613.3.3 (Eqn 16-38) Spectral Response Acceleration (I sec), SM1
5% Damped Design 0.764g Section 1613.3.4 (Eqn 16-39) Spectral Response Acceleration (short), Sos
5% Damped Design 0.437g Section 1613.3.4 (Eqn 16-40) Spectral Response Acceleration (1 sec), SDI
7.5.2 Table 7.5.2 presents additional seismic design parameters for projects located in Seismic
Design Categories of D through F in accordance with ASCE 7-10 for the mapped
maximum considered geometric mean (MCEG).
TABLE 7.5.2
2013 CBC SEISMIC DESIGN PARAMETERS
Parameter Value ASCE 7-10 Reference
Mapped MCE0 Peak Ground Acceleration, PGA 0.408g Figure 22-7
Site Coefficient, FroA 1.092 Table 11.8-1
Site Class Modified MCE0 0.445g Section 11.8.3 (Eqn 11.8-1) Peak Ground Acceleration, PGAM
7.5.3 Conformance to the criteria in Tables 7.5.1 and 7.5.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur if a large earthquake occurs. The primary goal of seismic design is to protect life,
not to avoid all damage, since such design may be economically prohibitive.
Project No. 07135-42-07 -14 -July 22, 2015
7.6 Preliminary Foundation Recommendations
7 .6.1 The following preliminary foundation recommendations are based on expected soil
conditions on the lot at the completion of the current grading operation. Modification to
these recommendations may be needed and can be provided in update reports once
finalized development plans are prepared and actual soil conditions at the completion of
the current grading operation are known.
7.6.2 The foundation recommendations that follow are for one-to four-story residential
structures and are separated into categories dependent on the thickness and geometry of
the underlying fill soils as well as the expansion index of the prevailing subgrade soils of a
particular building pad (or lot). Categories for each building pad or lot will be provided
after the completion of grading once fill thickness is known and expansion index testing
has been performed on finish grade soils.
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<S0 10:::D<20
T2:S0 or underlain by D2:20 alluvium
Expansion
Index (EI)
EI<S0
S0<EI::::90
90<El:::130
7.6.3 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 Minimum Footing Continuous Footing Interior Slab
Category Embedment Depth Reinforcement Reinforcement (inches)
I 12 Two No. 4 bars, 6x6-10/l 0 welded wire
one top and one bottom mesh at slab mid-point
II 18 Four No. 4 bars, No. 3 bars at 24 inches
two top and two bottom on center, both directions
III 24 Four No. 5 bars, No. 3 bars at 18 inches
two top and two bottom on center, both directions
Project No. 07135-42-07 -15 -July 22, 2015
7.6.4 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 12 inches and 24 inches for continuous and isolated
footings, respectively.
7.6.5 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.
7.6.6 Slabs that may receive moisture-sensitive floor coverings or may be used to store moisture-
sensitive materials should be underlain by a vapor retarder. The vapor retarder design should
be consistent with the guidelines presented in the American Concrete Institute's (ACI) Guide
for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-06). In
addition, the membrane should be installed in accordance with manufacturer's
recommendations and ASTM requirements, and in a manner that prevents puncture. The
project architect or developer should specify the vapor retarder based on the type of floor
covering that will be installed and if the structure will possess a humidity controlled
environment.
7.6.7 The project foundation engineer, architect, and/or developer should determine the
thickness of bedding sand below the slab. In general, 3 to 4 inches of sand bedding is
typically used. Geocon should be contacted to provide recommendations if the bedding
sand is thicker than 6 inches.
7.6.8 The foundation design engineer should provide appropriate concrete mix design criteria and
curing measures to assure proper curing of the slab by reducing the potential for rapid
moisture loss and subsequent cracking and/or slab curl. The foundation design engineer
should specify the concrete mix design and proper curing methods on the foundation plan. It
is critical that the foundation contractor understands and follows the recommendations
presented on the foundation plan.
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 2013 CBC has updated the design requirements for post-tensioned
foundation systems. The post-tensioned systems should be designed by a structural engineer
experienced in post-tensioned slab design and design criteria of the Post-Tensioning Institute
(PTI), Third Edition, as required by the 2013 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
Project No. 07135-42-07 -I 6 -July 22, 2015
7.6.10
7.6.11
7.6.12
should incorporate the geotechnical parameters presented in 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 II III
Thornthwaite 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
If the structural engineer proposes a post-tensioned foundation design method other than
the 2013 CBC:
• The 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.
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 at least 6 inches below the clean sand or crushed rock layer.
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
Project No. 07135-42-07 -17 -July 22, 2015
7.6.13
7.6.14
7.6.15
7.6.16
7.6.17
7.6.18
should design the foundation system to reduce the potential of edge lift occurring for the
proposed structures.
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.
Category I, II, or III foundations may be designed for an allowable soil bearing pressure of
2,000 pounds per square foot (psf) ( dead plus live load). This bearing pressure may be
increased by one-third for transient loads due to wind or seismic forces. The estimated
maximum total and differential settlement for the planned structures due to foundation
loads is 1-inch and ½-inch, respectively. Differential settlement is estimated to occur over
a span of 40 feet.
We expect primary settlement of existing fills is essentially complete. However, we
estimate that additional settlement as a result of hydro-consolidation to be approximately
0.2 to 0.3 percent of the total fill thickness. We expect hydro-consolidation to occur over a
20 year or more duration. We estimate a total fill settlement as a result of hydro-
consolidation to be 1-inch or less in areas where compacted fill exists. A more refined
estimate of total and differential fill thickness can be made once building locations on
individual sheet graded pads are known.
Foundations will need to be designed to accommodate estimated total and differential fill
settlement from both building loading and hydroconsolidation. In addition, building pads
on Lot 2 where alluvium was left in-place should incorporate the estimated liquefaction
settlement.
Isolated footings, including PT foundation systems where footings are not reinforced with
PT cables, should have the minimum embedment depth and width recommended for
conventional foundations (see Section 7.6.1 through 7.6.3) for a particular foundation
category. 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
for Category III. Where this condition cannot be avoided, the isolated footings should be
connected to the building foundation system with grade beams.
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,
Project No. 07135-42-07 -18 -July 22, 2015
7.6.19
7.6.20
consideration should be given to connecting patio slabs, which exceed five feet in width, to
the building foundation to reduce the potential for future separation to occur.
Special subgrade presaturation is not deemed necessary prior to placing concrete; however,
the exposed foundation-and slab-subgrade soil should be moisture conditioned, as
necessary, to maintain a moist condition as would be appropriate in any such concrete
placement.
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, 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.
• For fill slopes greater than 20 feet high, foundations should be extended to a depth
where the minimum horizontal distance is equal to H/3 (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. A
post-tensioned slab and foundation system or mat foundation system can be used
to help reduce potential foundation distress associated with slope creep and lateral
fill extension. 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 fill
slopes up to 30 feet in height, and cut slopes regardless of height. For swimming
pools located near the top of fill slopes greater than 30 feet in height, additional
recommendations may be required and Geocon Incorporated should be contacted
for a review of specific site conditions.
• Although other improvements that are relatively rigid or brittle, such as concrete
flatwork or masonry walls, may experience some distress if located near the top of
a slope, it is generally not economical to mitigate this potential. It may be possible,
however, to incorporate design measures that would permit some lateral soil
movement without causing extensive distress. Geocon Incorporated should be
consulted for specific recommendations.
Project No. 07135-42-07 -I 9 -July 22, 2015
•
7.6.21
7.6.22
7.6.23
The exterior flatwork recommendations provided herein assumes that the near surface soils
are very low to low expansive (EI::::. 50). Exterior slabs not subjected to vehicular traffic
should be a minimum of four inches thick and reinforced with 6 x 6-6/6 welded wire mesh.
The mesh should be placed in the middle of the slab. Proper mesh positioning is critical to
future performance of the slabs. The contractor should take extra measures to provide
proper mesh placement. Prior to construction of slabs, the upper 12 inches of subgrade
soils should be moisture conditioned at or slightly above optimum moisture content and
compacted to at least 90 percent of the laboratory maximum dry density per ASTM 1557.
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 still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of
concrete shrinkage cracks is independent of the supporting soil characteristics. The
occurrence may be reduced and/or controlled by: ( 1) limiting the slump of the concrete,
(2) proper concrete placement and curing, and by (3) the placement of crack control joints
at periodic intervals, in particular, where re-entrant slab comers occur.
Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
7.7 Preliminary Retaining Wall Recommendations
7.7.1 Retaining walls that are allowed to rotate more than 0.001H (where H equals the height of
the retaining portion of the wall) at the top of the wall 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 pcf. Where the backfill will be inclined at 2:1 (horizontal:vertical), an active
soil pressure of 50 pcf is recommended. Expansive soils should not be used as backfill
material behind retaining walls. All soil placed for retaining wall backfill should have an
Expansion Index less than 50.
7. 7 .2 Soil contemplated for use as retaining wall backfill, including import materials, should be
identified in the field prior to backfill. At that time Geocon Incorporated should obtain
samples for laboratory testing to evaluate its suitability. Modified lateral earth pressures
may be necessary if the backfill soil does not meet the required expansion index or shear
strength. City or regional standard wall designs, if used, are based on a specific active
lateral earth pressure and/or soil friction angle. In this regard, on-site soil to be used as
backfill may or may not meet the values for standard wall designs. Geocon Incorporated
Project No. 07135-42-07 -20 -July 22, 2015
•
should be consulted to assess the suitability of the on-site soil for use as wall backfill if
standard wall designs will be used.
7.7.3 Unrestrained walls will move laterally when backfilled and loading is applied. The amount
of lateral deflection is dependent on the wall height, the type of soil used for backfill, and
loads acting on the wall. The wall designer should provide appropriate lateral deflection
quantities for planned retaining walls structures, if applicable. These lateral values should
be considered when planning types of improvements above retaining wall structures.
7.7.4 Where walls are restrained from movement at the top, an additional uniform pressure of
8H psf should be added to the active soil pressure where the wall possesses a height of
8 feet or less and 12H where the wall is greater than 8 feet. For retaining walls subject to
vehicular loads within a horizontal distance equal to two-thirds the wall height, a surcharge
equivalent to 2 feet of fill soil should be added (unit weight 130 pcf).
7.7.5 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) is not recommended
where the seepage could be a nuisance or otherwise adversely affect the property adjacent
to the base of the wall. The above recommendations assume a properly compacted granular
(EI of less than 50) free-draining backfill material with no hydrostatic forces or imposed
surcharge load. Figure 7 presents a typical retaining wall drainage detail. If conditions
different than those described are expected, or if specific drainage details are desired,
Geocon Incorporated should be contacted for additional recommendations.
7.7.6 The structural engineer should determine the seismic design category for the project in
accordance with Section 1613 of the CBC. If the project possesses a seismic design
category of D, E, or F, retaining walls that support more than 6 feet of backfill should be
designed with seismic lateral pressure in accordance with Section 18.3.5.12 of the 2013
CBC. 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
base of the wall and zero at the top of the wall. A seismic load of 21 H should be used for
design. We used the peak ground acceleration adjusted for Site Class effects, PGAM, of
0.445g calculated from ASCE 7-10 Section 11.8.3 and applied a pseudo-static coefficient
of0.33.
7. 7. 7 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
Project No. 07135-42-07 -21 -July 22, 2015
below the base of the wall consists of compacted fill with an Expansion Index of less
than 90. The allowable soil bearing pressure can be increased by 300 psf and 500 psf for
each additional foot of foundation width and depth, respectively, up to a maximum
allowable soil bearing of 4,000 psf. The proximity of the foundation to the top of a slope
steeper than 3: 1 could impact the allowable soil bearing pressure. Therefore, Geocon
Incorporated should be consulted where such a condition is anticipated.
7.7.8 Resistance to lateral loads will be provided by friction along the base of the wall
foundation or by passive earth pressure against the side of the footing. Allowable
coefficients of friction of 0.35 are recommended for footings in compacted fill. Passive
earth pressure may be taken as 150 pcf for walls founded on a 2: 1 slope, and 300 pcf for
horizontal ground in front of the wall. 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 in areas not protected by floor slabs
or pavement should not be included in design for passive resistance.
7.7.9 The recommendations presented above are generally applicable to the design of rigid
concrete or masonry retaining walls having a maximum height of 8 feet. In the event that
walls higher than 8 feet are planned, Geocon Incorporated should be consulted for
additional recommendations.
7.8 Detention Basin and Bioswale Recommendations
7 .8.1 Any detention basins, bioswales and bio-remediation areas should be designed by the
project civil engineer and reviewed by Geocon Incorporated. Typically, bioswales consist
of a surface layer of vegetation underlain by clean sand. A subdrain should be provided
beneath the sand layer. Prior to discharging into the storm drain pipe, a seepage cutoff wall
should be constructed at the interface between the subdrain and storm drain pipe. The
concrete cut-off wall should extend at least 6-inches beyond the perimeter of the gravel-
packed subdrain system.
7.8.2 Distress may be caused to planned improvements and properties located hydrologically
downstream or adjacent to these devices. 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 and adjacent 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. Due to site soil and geologic
conditions, permanent bioswales and bio-remediation areas should be lined with an
Project No. 07135-42-07 -22 -July 22, 2015
impermeable barrier, such as a thick visqueen, to prevent water infiltration in to the
underlying compacted fill.
7.8.3 The landscape architect should be consulted to provide the appropriate plant
recommendations. If drought resistant plants are not used, irrigation may be required.
7 .9 Site Drainage and Moisture Protection
7 .9 .1 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 2013 CBC 1804.3 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.
7.9.2 In the case of basement walls or building walls retaining landscaping areas, a water-
proofing system should be used on the wall and joints, and a Miradrain drainage panel ( or
similar) should be placed over the waterproofing. The project architect or civil engineer
should provide detailed specifications on the plans for all waterproofing and drainage.
7.9.3 Underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks, and detected leaks should be repaired promptly. Detrimental soil
movement could occur if water is allowed to infiltrate the soil for prolonged periods of
time.
7.9.4 Adequate drainage provisions are imperative. Under no circumstances should water be
allowed to pond adjacent to footings. The building pads should be properly finish graded
after the buildings and other improvements are in place so that drainage water is directed
away from foundations, pavements, concrete slabs, and slope tops to controlled drainage
devices.
Project No. 07135-42-07 -23 -July 22, 2015
LIMITATIONS AND UNIFORMITY OF CONDITIONS
1. 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.
2. The recommendations of this report pertain only to the site investigated and are based upon
the assumption that the soil conditions do not deviate from those disclosed in the
investigation. If any variations or undesirable conditions are encountered during
construction, or if the proposed construction will differ from that anticipated herein, Geocon
Incorporated should be notified so that supplemental recommendations can be given. The
evaluation or identification of the potential presence of hazardous or corrosive materials was
not part of the scope of services provided by Geocon Incorporated.
3. This report is issued with the understanding that it is the responsibility of the owner or his
representative to ensure that the information and recommendations contained herein are
brought to the attention of the architect and engineer for the project and incorporated into the
plans, and the necessary steps are taken to see that the contractor and subcontractors carry
out such recommendations in the field.
4. The findings of this report are valid as of the present date. However, changes in the
conditions of a property can occur with the passage of time, whether they be due to natural
processes or the works of man on this or adjacent properties. In addition, changes in
applicable or appropriate standards may occur, whether they result from legislation or the
broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly
or partially by changes outside our control. Therefore, this report is subject to review and
should not be relied upon after a period of three years.
Project No. 07135-42-07 July 22, 2015
THE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY GOOGLE EARTH,
SUBJECT TO A LICENSING AGREEMENT. THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY; IT IS
NOT INTENDED FOR CLIENT'S USE OR RELIANCE AND SHALL NOT BE REPRODUCED BY CLIENT. CLIENT
SHALL INDEMNIFY, DEFEND AND HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULT
OF SUCH USE OR RELIANCE BY CLIENT.
VICINITY MAP
GEOCON
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GEOTECHNICAL ■ ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
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./&pi ........ Ml.1'0llfffflllM!tDIIOll-8'""d)
,.._,_,. •.••... .-. LOCATION OF OEOL0GIC CONTACT (---)
200 2S) 300
Jspi
3IIO
DISTANCE
400 4!50
GEOLOGIC CROSS-SECTION A-A'
SCALE: 1• = 50' (Vert.= Horiz.)
!500 550 eoo
0
-ao
eeo 700
GEOCON 1NCOIIPOIIATBD 0
GEOTECINCAl • l!N¥IIONMl!NIAI. • IMTHWS -.OIUINBlmlW•Will8JO,CAIJFCllt,Mffl21 · l"f1~
-W-.000-fAXW-l'IOJECTNO. 07135.42.07
FIGUlf 3
[)Alf 07 -22 -2015
~11_1.,.M.wt~, .... ~~~o.t:-~1......,_(1111~
ASSUMED CONDITIONS :
SLOPE HEIGHT
SLOPE INCLINATION
H = 40 feet
1.5 : 1 (Horizontal :
TOTAL UNIT WEIGHT OF SOIL
Vertical) "It = 130 pounds per cubic foot
ANGLE OF INTERNAL FRICTION q> = 32 degrees
APPARENT COHESION C = 300 pounds per square foot
NO SEEPAGE FORCES
ANALYSIS:
'Yc<t> = 'YtH tan4> EQUATION (3-3), REFERENCE 1 C
FS = NcfC EQUATION (3-2), REFERENCE 1
'YtH
Ac<t> = 10.8 CALCULATED USING EQ. (3-3)
Ncf = 27 DETERMINED USING FIGURE 10, REFERENCE 2
FS = 1.56 FACTOR OF SAFETY CALCULATED USING EQ. (3-2)
REFERENCES:
1 ...... Janbu, N., Stability Analysis of Slopes with Dimensionless Parameters, Harvard Soil Mechanics,
Series No. 46, 1954
2 ...... Janbu, N., Discussion of J.M. Bell, Dimensionless Parameters for Homogeneous Earth Slopes,
Journal of Soil Mechanics and Foundation Design, No. SM6, November 1967.
SLOPE STABILITY ANALYSIS -1.5: 1 CUT SLOPES
GEOCON 0 QUARRY CREEK -LOT 2
CARLSBAD, CALIFORNIA
INCORPORATED
GEOTECHNICAL ■ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900-FAX 858 558-6159
RM/ AML I I DSK/GTYPD DATE 07 -22 -2015 I PROJECT NO. 07135 -42 -07 I FIG. 4
Ptotted:07122/201511:21AM I By:ALVIN LADRILLONO I FIie Location:Y:\PROJECTS\07135-42-07 (Quarry Creek-R2)\DETAILS\Slope Stablllty Analyses-Cut (1.5-1).dwg
ASSUMED CONDITIONS :
SLOPE HEIGHT H = 50 feet
SLOPE INCLINATION 2: 1 (Horizontal : Vertical)
TOTAL UNIT WEIGHT OF SOIL 'Yt = 130 pounds per cubic foot
ANGLE OF INTERNAL FRICTION <t> = 30 degrees
APPARENT COHESION C = 300 pounds per square foot
NO SEEPAGE FORCES
ANALYSIS:
"yc<t, = 'YtH tan<J, EQUATION (3-3), REFERENCE 1
C
FS = NcfC EQUATION (3-2), REFERENCE 1
'YtH
Ac<t, = 12.5 CALCULATED USING EQ. (3-3)
Ncf = 35 DETERMINED USING FIGURE 10, REFERENCE 2
FS = 1.61 FACTOR OF SAFETY CALCULATED USING EQ. (3-2)
REFERENCES:
1 ...... Janbu, N., Stability Analysis of Slopes with Dimensionless Parameters, Harvard Soil Mechanics,
Series No. 46, 1954
2 ...... Janbu, N., Discussion of J.M. Bell, Dimensionless Parameters for Homogeneous Earth Slopes,
Journal of Soil Mechanics and Foundation Design, No. SM6, November 1967.
SLOPE STABILITY ANALYSIS -FILL SLOPES
GEOCON 0 QUARRY CREEK -LOT 2
CARLSBAD, CALIFORNIA
INCORPORATED
GEOTECHNICAL ■ ENVIRONMENT AL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHOt'-IE 858 558-6900-FAX 858 558-6159
RM/AML I I DSK/GTYPD DATE 07 -22 -2015 I PROJECT NO. 07135 -42 -07 I FIG. 5
Plotted:07/22/2015 11 :21AM I By:ALVIN LADRILLONO 1 FIie Locadon:Y:\PROJECTS\07135-42-07 (Quarry Creek· R2)\OETAILS\Slope Stability Analyses-Flll.dwg
ASSUMED CONDITIONS :
SLOPE HEIGHT
DEPTH OF SATURATION
SLOPE INCLINATION
SLOPE ANGLE
H =
z =
1.5: 1
yertical)
1 =
Infinite
3 feet
(Horizontal :
33.7 degrees
UNIT WEIGHT OF WATER
TOTAL UNIT WEIGHT OF SOIL
ANGLE OF INTERNAL FRICTION
APPARENT COHESION
'Yw = 62.4 pounds per cubic foot
'Yt = 130 pounds per cubic foot
<I> = 32 degrees
C = 300 pounds per square foot
SLOPE SATURATED TO VERTICAL DEPTH Z BELOW SLOPE FACE
SEEPAGE FORCES PARALLEL TO SLOPE FACE
ANALYSIS:
FS =
REFERENCES:
C + ('Y 1 -'Yw) Z cos2 i tan <I>
'Y1 Z sin i cos i
1 ...... Haefeli, R. The Stability of Slopes Acted Upon by Parallel Seepage, Proc.
Second International Conference, SMFE, Rotterdam, 1948, 1, 57-62
= 2.2
2 ...... Skempton, A. W., and F.A. Delory, Stability of Natural Slopes in London Clay, Proc.
Fourth International Conference, SMFE, London, 1957, 2, 378-81
SURFICIAL SLOPE STABILITY ANALYSIS -1.5: l SLOPE
GEOCON 0 QUARRY CREEK -LOT 2
CARLSBAD, CALIFORNIA
INCORPORATED
GEOTECHNICAL ■ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900-FAX 858 558-6159
RMIAML I I DSK/GTYPD DATE 07-22-2015 I PROJECT NO. 07135-42-07 I FIG. 6
Plotted:07/22/201511:20AM I By.ALVIN LADRILLONO I Fie Locatlon:Y:\PROJECTS\0713>42-07 (Quarry Creek-R2)\DETAILS\Slope Stabllty Anatyses-Surflclal (1,5-1),dwg
WATER PROOFING
PER ARCHITECT
2/3H
GROUND SURFACE\
RETAINING
WALL
2/3 H
GROUND SURFACE
DRAINAGE PANEL
(MIRADRAIN 6000
OR EQUIVALENT)
3/4" CRUSHED ROCK 12·7 ,.,.,..,. .... .J/ (1 CU.FT./FT.)
~~y ~i~~fi{;:R
"»~~~~~~.._I _ _. FOOTIN~~ 4" DIA. SCHEDULE 40
PERFORATED PVC PIPE
OR TOTAL DRAIN
EXTENDED TO
APPROVED OUTLET
NOTE:
DRAIN SHOULD BE UNIFORMLY SLOPED TO GRAVITY OUTLET
OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING
TEMPORARY BACKCUT
PER OSHA
MIRAFI 140N FILTER FABRIC
(OR EQUIVALENT)
OPEN GRADED
1" MAX. AGGREGATE
4" DIA. PERFORATED SCHEDULE
40 PVC PIPE EXTENDED TO
APPROVED OUTLET
RETAINING
WALL
2/3 H
GROUND SURFACE
DRAINAGE PANEL
(MIRADRAIN 6000
OR EQUIVALENT)
4" DIA. SCHEDULE 40
PERFORATED PVC PIPE
OR TOTAL DRAIN
EXTENDED TO
APPROVED OUTLET
NO SCALE
TYPICAL RETAINING WALL DRAIN DETAIL
GEOCON
INCORPORATED 0
GEOTECHNICAL ■ ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE· SAN DIEGO, CALIFORNIA 92121 • 297 4
PHONE 858 558-6900 • FAX 858 558-6159
RM/AML I I DSK/GTYPD
QUARRY CREEK -LOT 2
CARLSBAD, CALIFORNIA
DATE 07-22 -2015 I PROJECT NO. 07135 -42 -07 I FIG. 7
Plotted:07/22/2015 11:15AM I By:ALVIN LADRILLONO I FIie Locatlon:Y:\PROJECTS\07135-42-07 (Quany Creek-R2)\DETAILS\Typlcal Retaining Wall Drainage Detail (RWDD7A).dwg
•
APPENDIX
APPENDIX A
RECOMMENDED GRADING SPECIFICATIONS
FOR
QUARRY CREEK -LOT 2
CARLSBAD, CALIFORNIA
PROJECT NO. 07135-42-07
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. The recommendations contained
in the text of the Geo technical 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, and/or 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.
2.4 Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
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•
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 ¾ inch in size.
3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than
4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than
12 inches.
3.1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than ¾ inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
3.2 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
Consultant shall not be used in fills.
3.3 Materials used for fill, either imported or on-site, shall not contain hazardous materials as
defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9
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•
and 1 O; 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 ½ 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.
4.2 Asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility or in an acceptable area of the project evaluated by
Geocon and the property owner. 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.
GI rev. 07/2015
•
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: 1 (horizontal:vertical), or
where recommended by the Consultant, the original ground should be benched in
accordance with the following illustration.
TYPICAL BENCHING DETAIL
Finish Grade
Remove All
Unsuitable Material
As Recommended By
Consultant Slope To Be Such That
Sloughing Or Sliding
Does Not Occur
Original Ground
/ Finish Slope Surface
"B"
See Note 1 See Note 2
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.
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.
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•
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.
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.
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. 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.
GI rev. 07/2015
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.
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.
GI rev. 07/2015
,.
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.
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
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, 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
GI rev. 07/2015
•
•
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.
7. SUBDRAINS
7.1 The geologic units on the site may have permeability characteristics and/or fracture
systems that could be susceptible under certain conditions to seepage. The use of canyon
subdrains may be necessary to mitigate the potential for adverse impacts associated with
seepage conditions. Canyon subdrains with lengths in excess of 500 feet or extensions of
existing offsite subdrains should use 8-inch-diameter pipes. Canyon subdrains less than 500
feet in length should use 6-inch-diameter pipes.
GI rev. 07/2015
TYPICAL CANYON DRAIN DETAIL
~ / NA~-~.,..,..,..,..,.
NOTES:
1.,_..a.ttQi DIAMETER, saEDULE _, PVC PERFOAAT!!D PR FOR fU8
II EXCe88 OF 100-R:ET II DEPT110R A PIPE LENGTH OF LONGER THAN IIOO FEET.
2...-.trlNCH DIAME11:R, SOIEDULE 40 PIIC PERFORATED PIPE FOR Fl.LS
LESS THAN 11JO.ffET IN DEPTH OR A PIPE LENGTH IHOlnER nlAN 11011 FEET.
,////
BEDROCK
N!Jff:l'IIW._.0PN'EATCllfflE
ltWJ.-~llD.
IQ.-cl'HT/l'001'0P<W'IN
_____ ..,
-141N: 1011Eal.WAU!NT) l'I.TIRF-
NO SCALE
7.2 Slope drains within stability fill keyways should use 4-inch-diameter (or lager) pipes.
GI rev. 07/2015
•
TYPICAL STABILITY FILL DETAIL
NOTEI
DETAIL
FORIM~
MAJ'ERW.
1---DCAVATIIIAIX:UT AT t:1 INCUIM11DN (U.._..OTII_ NCJTml).
I .. ..JIAIIE OF IITABlllTY Fill TO IE 3 FEET INTO ~TlllfW.. MATEJML, aCFINO A-MUM~ NTO aDPE.
1.-STAKJTY Pa.I. TO Ill! COIIPDll!DO, PIO'M.Y C0YYiCT!0 CIIWLlM 1011..
4 .. ...ctallEYIJRAIW TO IIEAPPADYEII PE'A..:ATEDCHIIIIEY 0IWN PNB.l(MIWllWN GaDIOREQUIVMENT)
PACID~---aMNA"ELY20,_,.CINTallTOCINTaN#/041'WTWIIIE.CLCIMWCIIIMAY•~•
IIEEl'IIBEBEMDMBEl.
1....1'1.TBUIATI!NM. T0 IU14·1NCtt. 0PIMGWJ!D CIILJalBI 1'100(Elja.o■l!D INAPPR01/!D PLTBl,Aaa: IJl,IIMPI 1GIC).
8. . ...cou.ECTOR l'PE TO IE 4-INCH Ml-1111 IJIMETER, PEIIRlRATEI>, ~ l"IIC IIOEUU.E40 OR
IQIJIVAUNT,N#Daol'ID10-AT1 l"aCINTIINMJlolll0~0UIUT.
NO SCALE
7.3 The actual subdrain locations will be evaluated in the field during the remedial grading
operations. Additional drains may be necessary depending on the conditions observed and
the requirements of the local regulatory agencies. Appropriate subdrain outlets should be
evaluated prior to finalizing 40-scale grading plans.
7.4 Rock fill or soil-rock fill areas may require subdrains along their down-slope perimeters to
mitigate the potential for buildup of water from construction or landscape irrigation. The
subdrains should be at least 6-inch-diameter pipes encapsulated in gravel and filter fabric.
Rock fill drains should be constructed using the same requirements as canyon subdrains.
GI rev. 07/2015
..
7 .5 Prior to outletting, the final 20-foot segment of a subdrain that will not be extended during
future development should consist of non-perforated drainpipe. At the non-perforated/
perforated interface, a seepage cutoff wall should be constructed on the downslope side of
the pipe.
TYPICAL CUT OFF WALL DETAIL
FRONT VIEW
SIDE VIEW
'
~
Q/T-OA'-.&.
NOIICAI.E
NO IICAI.E
7.6 Subdrains that discharge into a natural drainage course or open space area should be
provided with a permanent headwall structure.
GI rev. 07/2015
•
TYPICAL HEADWALL DETAIL
FRONT VIEW
SIDE VIEW
r011r -
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7.7 The final grading plans should show the location of the proposed subdrains. After
completion of remedial excavations and subdrain installation, the project civil engineer
should survey the drain locations and prepare an "as-built" map showing the drain
locations. The final outlet and connection locations should be determined during grading
operations. Subdrains that will be extended on adjacent projects after grading can be placed
on formational material and a vertical riser should be placed at the end of the subdrain. The
grading contractor should consider videoing the subdrains shortly after burial to check
proper installation and functionality. The contractor is responsible for the performance of
the drains.
GI rev. 07/2015
•
8. OBSERVATION AND TESTING
8.1 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.
8.2 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.
8.3 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.
8.4 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.
8.5 We should observe the placement of subdrains, to check that the drainage devices have
been placed and constructed in substantial conformance with project specifications.
8.6 Testing procedures shall conform to the following Standards as appropriate:
8.6.1 Soil and Soil-Rock Fills:
8.6.1.1 Field Density Test, ASTM D 1556, Density of Soil In-Place By the
Sand-Cone Method.
GI rev. 07/2015
8.6.1.2 Field Density Test, Nuclear Method, ASTM D 6938, Density of Soil and
Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
8.6.1.3 Laboratory Compaction Test, ASTM D 1557, Moisture-Density
Relations of Soils and Soil-Aggregate Mixtures Using I 0-Pound
Hammer and I 8-Inch Drop.
8.6.1.4. Expansion Index Test, ASTM D 4829, Expansion Index Test.
9. PROTECTION OF WORK
9.1 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.
9.2 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.
10. CERTIFICATIONS AND FINAL REPORTS
10.1 Upon completion of the work, Contractor shall furnish Owner a certification by the Civil
Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of
elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot
horizontally of the positions shown on the grading plans. After installation of a section of
subdrain, 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.
10.2 The Owner is responsible for furnishing a final as-graded soil and geologic report
satisfactory to the appropriate governing or accepting agencies. The as-graded report
should be prepared and signed by a California licensed Civil Engineer experienced in
geotechnical engineering and by a California Certified Engineering Geologist, indicating
that the geotechnical aspects of the grading were performed in substantial conformance
with the Specifications or approved changes to the Specifications.
GI rev. 07/2015
4
LIST OF REFERENCES
Anderson, J. G., Synthesis of Seismicity and Geological Data in California, U.S. Geological Survey
Open-file Report 84-424, 1984, pp. 1-186.
Boore, D. M., and G. M Atkinson, Boore-Atkinson NGA Ground Motion Relations for the Geometric
Mean Horizontal Component of Peak and Spectral Ground Motion Parameters, Report Number
PEER 2007/01, May 2007.
Chiou, Brian S. J., and Robert R. Youngs, A NGA Model for the Average Horizontal Component of Peak
Ground Motion and Response Spectra, preprint for article to be published in NGA Special
Edition for Earthquake Spectra, Spring 2008.
Geocon Incorporated, Update Geotechnical Investigation, Quarry Creek, Carlsbad/Oceanside,
California, dated February 24, 2015 (Project No. 07135-42-05)
Geocon Incorporated, Update Geotechnical Investigation, Amended Reclamation Plan, Quarry Creek
Refined Alternative 3, Carlsbad, California, dated September 10, 2009 (Project No. 07135-
42-01).
Geocon Incorporated, Limited Geotechnical Investigation to Evaluate Hardrock Constraints for Quarry
Creek, Carlsbad, California, dated April 9, 2004 (Project No. 07135-42-0lB.
Geocon Incorporated, Preliminary Geotechnical Investigation, Quarry Creek IL Carlsbad/Oceanside,
California, dated February 24, 2015 (Project No. 07135-42-03).
Geocon Incorporated, Foundation Report, Quarry Creek Bridge, Carlsbad, California, dated August 21,
2014 (Project No. 07135-42-04A).
Geocon Incorporated, Geocon Incorporated, Final Report of Testing and Observation Services During
Site Grading, Quarry Creek, Carlsbad, California, dated April 4, 2013 (Project No. 07135-
42-02).
Geocon Incorporated, Final Report of Testing and Observation Services During Site Grading, Quarry
Creek, Oceanside, California, dated March 11, 2013 (Project No. 07135-42-02).
Geology and Mineral Resources of San Diego County, California, California Division of Mines and
Geology Publication, 1963.
Jennings, C. W., Fault Activity Map of California And Adjacent Areas with Locations and Ages of Recent
Volcanic Eruptions, California Geological Survey, formerly California Division of Mines and
Geology, 1994.
Larsen, E. S., Batholith and Associated Rocks of Corona, Elsinore and San Luis Rey Quadrangle
Southern California, Geological Society of America, Memoir 29, 1948.
Ploessel, M. R., and J.E. Slosson, Repeatable High Ground Accelerations From Earthquakes, California
Geology, September 1974.
Project No. 07135-42-07 July 22, 2015
...
LIST OF REFERENCES (Concluded}
Project Design Consultants, Mass Grading Plans for Quarry Creek, prepared by Project Design
Consultants, City of Carlsbad approval June 4, 2015.
Risk Engineering, EZ-FRISK, 2008.
SB&O, Inc., Exhibit for Quarry Creek, Planning Area "R-1" and "R-2 ", plot date July 15, 2015.
Tan, S.S., and M. P. Kennedy, Geologic Maps of the Northwestern Part of San Diego County,
California, California Division of Mines and Geology, DMG Open File 96-02, 1996.
Unpublished reports and maps on file with Geocon Incorporated.
United States Department of Agriculture, 1953 Stereoscopic Aerial Photographs.
USGS computer program, 2002 Interactive Deaggregation, http://egint.cr.usgs.gov/deaggint/2002/index.php.
USGS computer program, Seismic Hazard Curves and Uniform Hazard Response Spectra.
Wesnousky, S. G., Earthquakes, Quaternary Faults, and Seismic Hazards in California, Journal of
Geophysical Research, Vol. 91, No. B12, 1986, pp. 12, 587-12, 631.
Project No. 07135-42-07 July 22, 2015