HomeMy WebLinkAboutSDP 15-17; QUARRY CREEK; UPDATE GEOTECHNICAL REPORT; 2015-09-01UPDATE
GEOTECHNICAL REPORT
QUARRY CREEK
PLANNING AREA R-1
CARLSBAD, CALIFORNIA
RECEIVED
APR 19 -.2016
LAND DEVELOPMENT
ENGINEERING
PREPARED FOR
CHELSEA INVESTMENT CORPORATION
CARLSBAD, CALIFORNIA
SEPTEMBER 1, 2015
PROJECT NO. 07135-42-08
Rodney C. Mik
GE'2-533
tp allo.2533
GEOCON INCORPORATED
Emilio Alvarado
RCE 66915
EA:RCM:AS:dmc
(4/del) Addressee
GEOCON
INCORPORATED
GEOTECHNICAL U ENVIRONMENTAL. MATERIALS
Project No. 07135-42-08
September 1, 2015
Chelsea Investment Corporation
5993 Avenida Encinas, Suite 101
Carlsbad, California 92008
Attention: Mr. Ron Brockhoff
Subject: UPDATE GEOTECHNICAL REPORT
QUARRY CREEK PLANNING AREA R-1
CARLSBAD, CALIFORNIA
Dear Mr. Brockhoff:
In accordance with your request and approval of our proposal (LG-1 5287, dated August 6, 2015), we
have prepared this update geotechnical report for the proposed development of the subject project. An
update geotechnical report and addenda reports were prepared for the overall Quarry Creek
development by Geocon Incorporated. This report provides site-specific geotechnical information for
use in design and construction of the proposed development planned for Planning Area R-1.
We understand that the proposed development will consist of multi-family residential structures. The
planned buildings will be two-story, wood-frame structures supported by shallow foundation systems
with slab-on-grade. Additional improvements consist of underground utilities and surface parking.
The accompanying report presents the findings of our study, and conclusions and recommendations
pertaining to the geotechnical aspects of project development. Based on the results of this study, it is
our opinion that the subject project can be developed as planned provided that the recommendations
of this report are followed.
Should you have questions regarding this update report, or if we may be of further service, please
contact the undersigned at your convenience.
Very truly yours,
6960 Flanders Drive U San Diego, California 92121-2974 U Telephone 858.558.6900 0 Fox 858.558.6159
TABLE OF CONTENTS
PURPOSE AND SCOPE .1
PREVIOUS AND ONGOING SITE DEVELOPMENT . 1
SITE AND PROJECT DESCRIPTION................................................................................................2
SOIL AND GEOLOGIC CONDITIONS .............................................................................................2
4.1 Compacted Fill (Qcf)..................................................................................................................2
4.2 Previously Placed Fill (Opfi) .....................................................................................................3
4.3 Previously Placed Fill (Qpf2) .....................................................................................................3
4.4 Santiago Formation (Ts).............................................................................................................3
4.5 Salto Intrusive (Jspi)...................................................................................................................3
GROUNDWATER................................................................................................................................4
GEOLOGIC HAZARDS ......................................................................................................................4
6.1 Faulting.......................................................................................................................................4
6.2 Seismicity-Deterministic Analysis.............................................................................................4
6.3 Seismicity-Probabilistic Analysis...............................................................................................5
6.4 Liquefaction and Seismically Induced Settlement......................................................................6
6.5 Tsunamis and Seiches.................................................................................................................6
6.6 Landslides...................................................................................................................................6
CONCLUSIONS AND RECOMMENDATIONS................................................................................7
7.1 General........................................................................................................................................7
7.2 Soil Excavation and Characteristics ........................... . ................................................................ 8
7.3 Grading Recommendations........................................................................................................9
7.4 Bulking and Shrinkage Factors.................................................................................................11
7.5 Slope Stability...........................................................................................................................12
7.6 Seismic Design Criteria ................................................... .... ... ............ .... ..................................13
7.7 Foundation and Concrete Slab-On-Grade Recommendations..................................................14
7.8 Preliminary Flexible and Rigid Pavement Recommendations.................................................20
7.9 Retaining Walls and Lateral Loads...........................................................................................23
7.10 Slope Maintenance ......................................................................... . .......................................... 25
7.11 Low Impact Development (Bioswales, Permeable Pavement).................................................25
7.12 Site Drainage and Moisture Protection.....................................................................................26
7.13 Precise Grading and Foundation Plan Review .........................................................................27
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map (Map Pocket)
Figure 3, Geologic Cross Sections, A-A' and B-B' (Map Pocket)
Figure 4, Wall/Column Footing Dimension Detail
Figure 5, Typical Retaining Wall Drain Detail
APPENDIX A
RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
UPDATE GEOTECHNICAL REPORT
1. PURPOSE AND SCOPE
This report presents updated geotechnical recommendations for the proposed ultimate improvement
of Planning Area (PA) R-1 in the Quarry Creek development located in Carlsbad, California (see
Vicinity Map, Figure 1). The purpose of this report is to evaluate soil and geologic conditions within
the limits of the project, and provide geotechnical recommendations pertaining to development of the
property as proposed.
The scope of this update report included a review of:
Update Geotechnical Investigation, Quarry Creek, Carlsbad/Oceanside, California, prepared
by Geocon Incorporated, dated February 24, 2015 (Project No. 07135-42-05).
Mass Grading Plans for: Quarry Creek, Project No. CT 11-04, Drawing No. 484-5A,
prepared by Project Design Consultants, print date May 15, 2015.
Site Development Permit Plan for: Quarry Creek Planning Area R-1, prepared by SB&O
Incorporated, electronic version received August 10, 2015.
The recommendations presented herein are based on analysis of the data and observations obtained
during the overall Quarry Creek development, previous investigation, and our experience with similar
soil and geologic conditions. Additional references reviewed to prepare this report are provided in the
List of References section of this report.
2. PREVIOUS AND ONGOING SITE DEVELOPMENT
The Quarry Creek property has undergone many years of mining, crushing, and screening to produce
commercial aggregate products. Reclamation grading of the previously mined area commenced in
July 2011 and was completed in December 2012. Specifically across the limits of the subject
planning area, grading resulted in a partially sheet-graded pad with the north portion of the property
remaining in an ungraded condition.
Grading is currently occurring across the Quarry Creek development under our testing and
observation services. Based on the referenced mass grading and project site plan, grading of PA R-1
will result in a sheet-graded pad with ascending slopes along the north and east margins of the
property. We will prepare an as-graded report after completion of the ongoing grading operations that
will include laboratory test results as well as professional opinions pertaining to the current mass
grading operation.
Project No. 07135-42-08 - 1 - September 1, 2015
SITE AND PROJECT DESCRIPTION
Planning Area R-1 is located at the northeastern portion of the Quarry Creek development. The
project is bound by Haymar Drive to the north, Lot 2 to the west, Buena Vista Creek to the south, and
commercial development the east.
Based on the discussion in Section 2 above, the anticipated as-graded condition of the subject property
at completion of current grading will consist of compacted fill, Santiago Formation, and Salto Intrusive
rock exposed at grade. The sheet-graded pad portion of the lot will slope from northeast to southwest
with elevations varying from approximately 114 Mean Sea Level (MSL) to 118 MSL.
We understand that the proposed development will consist of fine grading the property to
accommodate two-story multi-family structures. Based on the site development plan, fine grading will
consist of placing up to four feet of fill to achieve ultimate design grades. Additional improvements
will consist of underground utilities, surface parking and park area. The buildings will consist of
wood-frame construction supported by conventional continuous and isolated spread footings with
slab-on-grade or post-tensioned slabs.
The descriptions provided herein are based on a review of available information including previous
geotechnical reports prepared for the property and the site plan/conceptual grading plan prepared by
SB&O Incorporated. If project details vary significantly from those outlined herein, Geocon
Incorporated should be notified for review and possible revisions to this report.
SOIL AND GEOLOGIC CONDITIONS
Previous and ongoing grading operations being performed for the overall Quarry Creek development
will result with compacted fill, Santiago Formation, and Salto Intrusive rock at grade across the
subject project. These units are described below and their approximate lateral extent is shown on the
Geologic Map (Figure 2) and the Geologic Cross Section Map (Figure 3).
4.1 Compacted Fill (Qcf)
Compacted fill was placed during previous grading and is being placed during current grading
operations. In areas of fill, grading should result in an approximately three foot-thick soil cap with few
six-inch minus rock. The fill soils generally consist of silty to clayey, fine to medium sand with
varying amounts of rock fragments, soil-rock fills, and windrows of oversize rock and concrete. Rock
greater than 12 inches was placed approximately 10 feet below finish sheet-grade. Although
particular attention was given to restricting material placement to the criteria described above, some
oversize rocks (material >12 inches) could be present in the upper portions of the fill areas. Based on
information presented in Reference No. 1 and in-place density testing performed on the current
Project No. 0713542-08 -2- September 1, 2015
grading operation, the fill is compacted to at least 90 percent of the laboratory maximum dry density
at or slightly above the optimum moisture content. We anticipate that ultimate development will
commence in several months. Excluding the upper approximately one foot that will undergo drying
and wetting due to the climate, the compacted fill is suitable for support of additional fill and/or
structural loading.
4.2 Previously Placed Fill (Qpfi)
Previously placed fill extends into the east portion of the property and underlies the compacted fill.
Ninyo and Moore provided testing and observation services during placement of this fill between
approximately 1988 and 2000. The fill was compacted to at least 90 percent relative compaction near
to slightly above optimum moisture content as indicated in the report prepared by Nino and Moore
dated August 2000. The fill is suitable for support of additional fill and/or structural loading. We do
not anticipate that planned improvements will extend into the previously compacted fill.
4.3 Previously Placed Fill (Qpf2)
Previously placed fill associated with Haymar Drive and State Route 78 is located along the
northwest margin of the lot. An as-graded report specific to this grading was not available for our
review. Based on our field observations, the fill is generally medium dense and moist. These soils
should not impact ultimate development of the subject project.
4.4 Santiago Formation (Ts)
The Eocene-aged Santiago Formation, consisting of dense, massive bedded light brown to greenish-
gray sandstones with thin claystone and siltstones interbeds. 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. Where practical, clayey materials of the
Santiago Formation should be placed at least three feet below proposed finish grade. The formation
underlies the compacted fill and is exposed at finish grade along the north portion of the property.
4.5 Salto intrusive (Jspi)
The Jurassic-aged Salto Intrusive consists of a steeply jointed, dark gray, very strong tonalite to
gabbro rock considered to be older than the Peninsular Range Batholith and more closely related to
the formation of the Santiago Peak Volcanics (Larsen, 1948). The bedrock is exposed at grade in the
central portion of the lot and also underlies the compacted fill. Exploratory excavations encountered
mostly buried intrusive rock that exhibited a variable weathering pattern ranging from highly
weathered and fractured material near contacts with the overlying sedimentary rocks, to fresh,
extremely strong crystalline rock within quarried areas.
Project No. 0713542-08 -3 - September 1, 2015
5. GROUNDWATER
Groundwater was encountered in the drainage areas of Buena Vista Creek and its tributaries at
elevations between 70 to 80 feet MSL. Depth of groundwater is subject to fluctuation from natural
seasonal variations. Groundwater is not anticipated to impact proposed project development.
However, it is not uncommon for groundwater or seepage conditions to develop where none
previously existed. Groundwater or seepage is dependent on seasonal precipitation, irrigation, land
use, among other factors, and vary as a result. Proper surface drainage will be important to future
performance of the project.
6. GEOLOGIC HAZARDS
6.1 Faulting
Review of geologic literature, geotechnical reports prepared for the property by Geocon Inc. and
others, and observations during previous field investigations indicate no active or potentially active
faults traverse the property. One fault was observed in the Salto Intrusive rock across the quarry slope
located along the central portion of the 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.
6.2 Seismicity-Deterministic Analysis
We used the computer program EZ-FRISK (Version 7.65) to determine the distance of known faults
to the site and to estimate ground accelerations at the site for the maximum anticipated seismic event.
According to the computer program EZ-FRISK (Version 7.65), 10 known active faults are located
within a search radius of 50 miles from the site. We used acceleration attenuation relationships
developed by Boore-Atkinson (2008) NGA USGS 2008, Campbell-Bozorgnia (2008) NGA USGS
2008, and Chiou-Youngs (2007) NGA USGS 2008 in our analysis. The nearest known active fault is
the Newport-Inglewood/Rose Canyon Fault, located approximately eight miles west of the site and is
the dominant source of potential ground motion. Table 6.2 lists the estimated maximum earthquake
magnitude and peak ground acceleration for faults in relationship to the site location calculated for
Site Class D as defined by Table 1613.3.2 of the 2013 California Building Code (CBC).
Project No. 07135-42-08 -4- September 1, 2015
TABLE 6.2
DETERMINISTIC SPECTRA SITE PARAMETERS
Fault Name
Distance
from Site
(miles)
Maximum
Earthquake
Magnitude
(Mw)
Peak Ground Acceleration '
Boore-
Atkinson
2008(g)
Campbell-
Bozorgnia
2008(g)
Chiou-
Youngs
2007(g)
Newport-Inglewood/Rose Canyon 8 7.5 0.29 0.25 0.32
Rose Canyon 8 6.9 0.25 0.23 0.26
Elsinore . 20 7.85 0.22 0.15 0.20
Coronado Bank 24 7.4 0.17 0.12 0.14
Palos Verdes Connected 24 7.7 0.19 0.13 0.16
San Joaquin Hills 36 7.1 0.12 0.10 0.09
Palos Verdes 36 7.3 0.13 0.08 0.09
Earthquake Valley 41 6.8 0.09 0.06 0.05
San Jacinto 44 7.88 0.13 0.09 0.11
Chino 1 46 6.8 0.08 0.06 0.05
6.3 Seismicity-Probabilistic Analysis
We performed a probabilistic seismic hazard analysis using the computer program EZ-FRISK. The
program 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 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 USGS 2008, Campbell-Bozorgnia (2008) NGA USGS
2008, and Chiou-Youngs (2007) NGA USGS 2008 in the analysis. Table 6.3 presents the site-specific
probabilistic seismic hazard parameters including acceleration-attenuation relationships and the
probability of exceedence.
Project No. 0713542-08 -5- September 1, 2015
TABLE 6.3
PROBABILISTIC SEISMIC HAZARD PARAMETERS
Probability of Exceedence
Peak Ground Acceleration
Boo re-Atkinson,
2008 (g)
Campbell-Bozorgnia,
2008 (g)
Chiou-Youngs,
2007 (g)
2% in a 50 Year Period 0.51 0.41 0.48
5% in a 50 Year Period 0.39 0.32 0.36
10% in a 50 Year Period 0.31 0.25 0.27
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 frequency and duration of
motion and soil conditions underlying the site. Seismic design of the structures should be evaluated in
accordance with the CBC guidelines or those currently adopted by the City of Carlsbad.
6.4 Liquefaction and Seismically Induced Settlement
The risk associated with liquefaction and seismically induced settlement hazard at the subject project
is very low due to the existing dense to very stiff compacted fill, very dense to hard nature of the
Santiago Formation and Salto Intrusive rock, and the lack of a permanent, shallow groundwater table.
6.5 Tsunamis and Seiches
The risk associated with tsunamis and seiches hazard at the project is very low due to the large distance
from the coastline and the absence of an upstream body of water.
6.6 Landslides
No landslides were encountered within the site or mapped within the immediate areas influencing the
project development. The risk associated with landslide hazard is very low.
Project No. 07135-42-08 -6- September 1, 2015
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 No soil or geologic conditions were encountered during this study that would preclude the
development of the property as presently planned provided the recommendations of this
report are followed.
7.1.2 The existing compacted fill soils, Santiago Formation, and the Salto Intrusive rock are
considered suitable for support of additional fill or structural loads. In areas where fill is
required to achieve ultimate pad grade, the upper one foot of the existing ground surface
should be scarified, moisture conditioned, mixed and compacted prior to placing fill.
7.1.3 Based on the planned finish pad grades shown on the site/conceptual grading plan and the
estimated as-graded condition of the sheet-graded pad portion of PA R-1, we do not
anticipate that grading will result with a fill to formation transition condition across the
planned building pads.
7.1.4 Excavations within the Salto Intrusive rock may generate oversize rock (material
>12 inches) that will require special placement within fill areas and/or exportation from the
project due to limited fill volume.
7.1.5 The Santiago Formation has clayey siltstone and claystone layers that are typically
moderate to high expansive materials. If encountered, high expansive soils should be
placed at least three feet below proposed ultimate subgrade elevations.
7.1.6 Depending on the time of year that fine grading is performed, wet to saturated soil
conditions may be encountered. Wet soils, if encountered, will need to be dried or mixed
with dryer soil to facilitate proper compaction.
7.1.7 Imported soils, if required, should have an Expansion Index (El) 5O. Geocon Incorporated
should be notified of the import source and should perform laboratory testing prior to
arrival to determine its suitability as fill material.
7.1.8 The on-site geologic units have permeability characteristics and/or fracture systems that are
conducive to water transmission, natural or otherwise (e.g., landscape), and may result in
future seepage conditions. It is not uncommon for groundwater or seepage conditions to
develop where none previously existed, particularly after landscape irrigation is initiated.
The occurrence of induced groundwater seepage from landscaping can be greatly reduced
by implementing and monitoring a landscape program that limits irrigation to that
Project No. 07135-42-08 -7- September 1, 2015
sufficient to support the vegetative cover without over watering. Shallow subdrains may be
required in the future if seeps occur after rainy periods or after landscaping is installed.
7.2 Soil Excavation and Characteristics
7.2.1 We expect that the compacted fill can be excavated with a light to moderate effort with
conventional heavy duty grading equipment. We anticipate that excavations in the Santiago
Formation will require a moderate to heavy effort. Excavations in the slightly weathered to
fresh Salto Intrusive rock may require blasting or specialized rock breaking techniques to
efficiently excavate and handle the rock. Oversize material (material >12 inches) may be
generated which would require special handling or exportation from the site.
7.2.2 We expect on-site soil to be "expansive" (Expansion Index [El] ?20) as defined by 2013
California Building Code (CBC) Section 1803.5.3. For fill areas, we anticipate that the
mass grading operation should result with a three foot soil cap across the sheet-graded pad
portion of the lot possessing an expansion potential of very low to medium (20 <El 90) in
accordance with ASTM D 4829. Table 7.2.1 presents soil classifications based on ASTM
classification and the CBC. We will present laboratory test results in an addendum report
after completion of the ongoing mass grading operation. Additionally, soil sampling and
testing should be performed on fill soils after completion of fine grading operations to
evaluate the expansive potential of the near surface soils.
TABLE 7.2.1
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
ASTM 4829 AND 2013 CBC
Expansion Index (El) Expansion Classification
ASTM 4829
2013 CBC
Expansion Classification
0-20 Very Low Non-Expansive
21-50 Low
Expansive
Very High
51-90 Medium
91-130 High
Greater Than 130
7.2.3 We recommend that guidelines presented in the 2013 CBC Section 1904 and ACI 318
Sections 4.2 and 4.3 be followed in determining the type of concrete to be used. Table 7.2.2
presents a summary of concrete requirements set forth by the CBC and AC!. 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
Project No. 0713542-08 -8- September 1, 2015
concentration. Based on the discussion above and during fine grading operations,
additional soil sampling and testing should be performed on fill soils located near finish
pad grade to evaluate water-soluble sulfate content.
TABLE 7.2.2
REQUIREMENTS FOR CONCRETE EXPOSED TO SULFATE-CONTAINING SOLUTIONS
Water-Soluble Maximum Minimum Sulfate Exposure Sulfate Cement Water to Compressive Exposure Class Percent Type Cement Ratio Strength (psi) by Weight by Weight
Negligible SO 0.00-0.10 - -- 2,500
Moderate Si 0.10-0.20 11 0.50 4,000
Severe S2 0.20-2.00 V 0.45 4,500
Very Severe S3 >2.00 V+Pozzolan
or 0.45 4,500 Slag
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 Grading Recommendations
7.3.1 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.
7.3.2 Prior to commencing grading, a preconstruction conference should be held at the site with
the owner or developer, grading contractor, civil engineer, and geotechnical engineer in
attendance. Special soil handling and the grading plans can be discussed at that time.
7.3.3 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 check in-place dry density and moisture content.
7.3.4 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.
Project No. 07135-42-08 -9- September 1, 2015
7.3.5 Areas to receive fill should be scarified to a depth of at least 12 inches, moisture
conditioned as necessary, and compacted to at least 90 percent relative compaction prior to
placing additional fill. In areas where proposed cuts into existing fills are less than
12 inches, the resulting finish-grade soils should be scarified at least 12 inches, moisture
conditioned as necessary, and compacted to at least 90 percent relative compaction. Near-
surface soils may need to be processed to greater depths depending on the amount of
drying or wetting that has occurred since initial sheet-grading operations. The actual extent
of remedial grading should be determined in the field by the geotechnical engineer or
engineering geologist. Overly wet surficial soils, if encountered, will need to be removed to
expose existing dense/very stiff, moist compacted fill, Santiago Formation, or Salto
Intrusive rock,.The wet soils will require drying and/or mixing with drier soils to facilitate
proper compaction.
7.3.6 After site preparation and removal of unsuitable soils as described above is performed, 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 provided vegetation,
debris and other deleterious matter are removed. Layers of fill should be no thicker than
will allow for adequate bonding and compaction. Fill, including backfill and scarified
ground surfaces, should be compacted to at least 90 percent of laboratory maximum dry
density as determined by ASTM D 1557, at or slightly above optimum moisture content.
The project geotechnical engineer may consider fill materials below the recommended
minimum moisture content unacceptable and may require additional moisture conditioning
prior to placing additional fill.
7.3.7 Where practical and if select soil is available on-site, the upper three feet of building pads
and 12 inches in pavement areas should be composed of properly compacted fill or
undisturbed formational very low to low (El S50) expansive soils. Medium expansive soils
(El s90) may also be used to achieve design grades.
7.3.8 We anticipate that graded areas may result with Salto Intrusive rock near finish grade. The
presence of hard rock may impact future development. We recommend hard rock be
undercut to a depth of at least three feet below finish pad grade or one foot below deepest
foundation element, whichever is deeper. Also, consideration should be given to
undercutting bedrock at least two feet below the deepest underground utility in
streets/driveways. Undercut areas should be replaced with compacted low expansive
(El S50) soil fill, if available. As a minimum, fill should consist of medium expansive soil
(EI90).
Project No. 07135-42-08 -10- September 1, 2015
7.3.9 Excavations within the Santiago Formation may encounter high expansive (90 <El 130)
materials. If encountered within three feet of design grade within the limits of planned
surface improvements, consideration should be given to undercutting the high expansive
soil at least three feet below design grades. The undercut should be performed as
recommended in Section 7.3.10.
7.3.10 Undercuts (overexcavations) performed on hard rock or expansive soil materials 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.
7.3.11 Rocks, concretions or irreducible material greater than six inches in maximum dimension
should not be placed within three feet of finish grade in graded areas. Rocks greater than
12 inches in maximum dimension should not be placed within the upper five feet of finish
grade and two feet below the deepest utility. Placement of the oversize rock should be
performed in accordance with the recommendations in Appendix A. Some oversize rocks
may need to be exported from the project due to limited fill volume.
7.3.12 We recommend that excavations be observed during grading by a representative of Geocon
Incorporated to check that soil and geologic conditions do not differ significantly from
those anticipated.
7.3.13 In order to maintain safety and the stability of adjacent improvements, it is the
responsibility of the contractor to ensure that all excavations and trenches are properly
shored and maintained in accordance with the applicable OSHA rules and regulations.
7.3.14 Imported materials (if required) to achieve planned grading elevations, should consist of
granular very low to low expansive soils (El s50). Prior to importing the material, samples
from proposed borrow areas should be obtained and subjected to laboratory testing to
evaluate if the material conforms to the recommended criteria. The import soil should be
free of rock greater than six inches and construction debris. Laboratory testing typically
takes up to four days to complete. The grading contractor needs to coordinate the
laboratory testing into the schedule to provide sufficient time to allow for completion of
testing prior to importing materials.
7.4 Bulking and Shrinkage Factors
7.4.1 Estimates of embankment bulking and shrinkage factors are based on comparing laboratory
compaction tests with the density of the material in its natural or compacted state. It should
Project No. 07135-42-08 -11- September 1, 2015
be emphasized that the variations in natural soil density, as well as compacted fill densities,
render shrinkage value estimates very approximate. As an example, the contractor can
compact the fill soils to any relative compaction greater than 90 percent of the laboratory
maximum dry density. Thus, the contractor has approximately a 10 percent range of control
over the fill volume. Based on the findings of this study and experience on nearby or
adjacent projects with similar soil conditions, the following embankment factors can be
used as a basis for estimating how much the on-site soils may shrink or bulk when
excavated from their present condition and placed as compacted fill.
TABLE 7.4
Soil Unit Shrink/Bulk Factor
Existing Compacted Fill N/A
Santiago Formation 5 to 10 percent bulk
Salto Intrusive Rock (slightly weathered to fresh) 15 to 20 percent bulk
7.5 Slope Stability
7.5.1 Slope stability analyses were previously performed on the 2:1 fill and cut slopes for the
overall Quarry Creek development (see referenced update geotechnical report dated
February 24, 2015). The deep-seated and surficial slope stability analyses where performed
using the simplified Janbu analysis using average drained direct shear strength parameters
based on laboratory tests performed during our previous geotechnical investigation. The
results of the analysis indicate that cut and fill slopes have a factor-of-safety of at least 1.5
against deep seated and surficial instability for the slope heights proposed.
7.5.2 No new significant slopes are planned for this phase of grading. We expect that interior fill
and cut slopes with inclinations of 2:1 (horizontal:vertical) or flatter and maximum heights
of approximately three feet will be constructed during fine grading operations. The existing
and planned slopes at the project will possess a factor of safety greater than 1.5 against
deep-seated and surficial failure.
7.5.3 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 (El S90) to reduce the
potential for surficial sloughing.
7.5.4 Fill slopes 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.
Project No. 07135-42-08 -12- September 1, 2015
7.5.5 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.
7.6 Seismic Design Criteria
7.6.1 We used the computer program US. Seismic Design Maps, provided by the USGS.
Table 7.6.1 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. Structures founded on compacted fill with thickness
of 10 feet or less should be designed using a Site Class C. Structures founded on fill soil
with thickness greater than 10 feet should be designed using Site Class D. We evaluated the
Site Class based on the discussion in Section 16 13.3.2 of the 2013 CBC and Table 20.3-1
of ASCE 7-10. The values presented in Table 7.6.1 are for the risk-targeted maximum
considered earthquake (MCER). Final site class recommendations for each building will be
provided in our as-graded report at the completion of fine grading operations.
TABLE 7.6.1
2013 CBC SEISMIC DESIGN PARAMETERS
Parameter Site Class 2013 CBC
Reference
Site Class C D Table 1613.5.2
Spectral Response - Class B (0.2 sec), Ss 1.064 g 1.064 g I Figure 1613.5(3)
Spectral Response — Class B(1 sec),Si 0.412g 0.412g Figure 1613.5(4)
Site Coefficient, Fa 1.000 1.074 Table 1613.5.3(1)
Site Coefficient, F 1.388 1.588 Table 1613.5.3(2)
Maximum Considered Earthquake 1.064g 1.143g Section 1613.5.3
Spectral Response Acceleration (0.2 sec), SMS (Eqn 16-36)
Maximum Considered Earthquake 0.572 g 0.655 g Section 1613.5.3
Spectral Response Acceleration(1 sec), SMI (Eqn 16-37)
5% Damped Design 0.709 g 0.762 g Section 1613.5.4
Spectral Response Acceleration (0.2 sec), SDS (Eqn 16-38)
5% Damped Design 0.3819 0.436 g Section 1613.5.4
Spectral Response Acceleration (1 sec), SDI (Eqn 16-39)
Project No. 07135-42-08 -13- September 1, 2015
7.6.2 Table 7.6.2 presents additional seismic design parameters for projects located in Seismic
Design Categories of C through D in accordance with ASCE 7-10 for the mapped
maximum considered geometric mean (MCE6).
TABLE 7.6.2
2013 CBC SEISMIC DESIGN PARAMETERS
Site Class Parameter ASCE 7-10 Reference ___________
C
___________
D
Mapped MCE0 0.406 g 0.406 g Figure 22-7 Peak Ground Acceleration, PGA
Site Coefficient, FPGA 1.000 1.094 Ta1le 11.8-1
Site Class Modified MCE0 0.406 g 0.444 g Section 11.8.3 (Eqn 11.8-1) Peak Ground Acceleration, PGAM
7.6.3 Conformance to the criteria 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.
7.7 Foundation and Concrete Slab-On-Grade Recommendations
7.7.1 The foundation recommendations that follow are for one- to three-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 ultimate (fine) grading once fill thickness is known and expansion
index testing has been performed on finish grade soils.
TABLE 7.7.1
FOUNDATION CATEGORY CRITERIA
Foundation
Category
Maximum Fill
Thickness, T (feet)
Differential Fill
Thickness, D (feet)
Expansion
Index (El)
I T<20 -- El <50
II 20r<50 10 <D <20 50<EI$90
ifi T?50 D20 90<EI130
7.7.2 Table 7.7.2 presents minimum foundation and interior concrete slab design criteria for
conventional foundation systems.
Project No. 07135-42-08 -14- September 1, 2015
TABLE 7.7.2
CONVENTIONAL FOUNDATION RECOMMENDATIONS BY CATEGORY
Foundation Minimum Footing
Embedment Depth Continuous Footing Interior Slab
Category
(inches)
Reinforcement Reinforcement
I 12 Two No. 4 bars, 6x6-10/1O 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
7.7.3 The embedment depths presented in Table 7.7.2 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. A wall/column footing dimension detail is presented on Figure 4.
7.7.4 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 ifi.
7.7.5 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 (AC!) Guide
for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (AC! 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.
7.7.6 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.
7.7.7 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
Project No. 07135-42-08 -15- September 1, 2015
is critical that the foundation contractor understands and follows the recommendations
presented on the foundation plan.
7.7.8 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
(PT!), 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
should incorporate the geotechnical parameters presented in Table 7.7.3 for the particular
Foundation Category designated. The parameters presented in Table 7.7.3 are based on the
guidelines presented in the PTI, Third Edition design manual.
TABLE 7.7.3
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI)
Third Edition Design Parameters
Foundation Category
1 11 in
Thomthwaite Index -20 -20 -20
Equilibrium Suction 3.9 3.9 3.9
Edge Lift Moisture Variation Distance, em (feet) 5.3 5.1 4.9
Edge Lift, yM (inches) 0.61 1.10 1.58
Center Lift Moisture Variation Distance, CM (feet) 9.0
PI0.30
9.0 9.0
Center Lift, yM (inches) 0.47 0.66
7.7.9 If the structural engineer proposes a post-tensioned foundation design method other than
PTI, Third Edition:
The criteria presented in Table 7.7.3 are still applicable.
Interior stiffener beams should be used for Foundation Categories II and ifi.
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 ifi, respectively. The embedment
depths should be measured from the lowest adjacent pad grade.
7.7.10 The foundations for the post-tensioned slabs should be embedded in accordance with the
recommendations of the structural engineer. For moisture cut-off, we recommend the
Project No. 0713542-08 -16- Septembei 1, 2015
perimeter foundation have an embedment depth of at least 12 inches. If a post-tensioned
mat foundation system is planned, the slab should possess a thickened edge with a
minimum width of 12 inches that extends below the clean sand layer.
7.7.11 Our experience indicates post-tensioned slabs are susceptible to excessive edge lift,
regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the
perimeter footings and the interior stiffener beams may mitigate this potential. Current PTI
design procedures primarily address the potential center lift of slabs but, because of the
placement of the reinforcing tendons in the top of the slab, the resulting eccentricity after
tensioning reduces the ability of the system to mitigate edge lift. The structural engineer
should design the foundation system to reduce the potential of edge lift occurring for the
proposed structures.
7.7.12 During the construction of the post-tension foundation system, the concrete should be
placed monolithically. Under no circumstances should cold joints form between the
footings/grade beams and the slab during the construction of the post-tension foundation
system.
7.7.13 Footings proportioned as recommended above may be designed for an allowable soil
bearing pressure of 2,000 pounds per square foot (psi). For foundations exceeding the
minimum width and embedment presented in Sections 7.7.2 and 7.7.3, the soil bearing
pressure may 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 pressure of 3,500
psf. The allowable bearing pressure is for dead plus live loads and may be increased by up
to one-third when considering transient loading such as those due to wind or seismic
forces.
7.7.14 Estimated total and differential settlement of footings imposing the above bearing pressures
and bearing on compacted fill is 1 inch and 3h inch, respectively. Differential settlement is
estimated to occur over a span of 40 feet.
7.7.15 We expect primary settlement of existing fills will essentially be completed prior to
construction of structures. However, we estimate that additional settlement of the deeper
fills across the southern half of property 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.
Project No. 07135-42-08 -17- September 1, 2015
7.7.16 The foundation systems for the planned structures should be designed to accommodate the
estimated total and differential settlement of the supporting fill soil due to imposed
structural loading and hydro-compression. We estimate fill differential for static loading
and hydro-compression to be 1 inch over a span of 40 feet.
7.7.17 Isolated footings, if present, should have the minimum embedment depth and width
recommended for conventional foundations. 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 ifi. Where this condition cannot be avoided,
the isolated footings should be connected to the building foundation system with grade
beams.
7.7.18 For Foundation Category III, consideration should be given to using interior stiffening
beams and connecting isolated footings and/or increasing the slab thickness. In addition,
consideration should be given to connecting patio slabs, which exceed five feet in width, to
the building foundation to reduce the potential for future separation to occur.
7.7.19 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.
7.7.20 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 H13 (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.
Project No. 0713542-08 -Is- September 1, 2015
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.
7.7.21 The exterior fiatwork recommendations provided herein assumes that grading is performed
as recommended above and that the near surface soils are very low to medium expansive
(El S90). Exterior slabs not subjected to vehicular traffic should be a minimum of four
inches thick and reinforced with 6x6-W2.91W2.9 (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 one to three percent above optimum moisture content and
compacted to at least 90 percent of the laboratory maximum dry density per ASTM 1557.
7.7.22 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 corners occur.
7.7.23 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
7.7.24 Foundation excavations should be observed by the geotechnical engineer (a representative
of Geocon Incorporated) prior to the placement of reinforcing steel and concrete to check
that the exposed soil conditions are consistent with those anticipated and that footings have
Project No. 0713542-08 -19- September 1, 2015
been extended to appropriate bearing strata. If unanticipated soil conditions are
encountered, foundation modifications may be required.
7.8 Preliminary Flexible and Rigid Pavement Recommendations
7.8.1 The following preliminary pavement design sections are based on our experience with soil
conditions within the surrounding area and laboratory test results performed during the
overall Quarry Creek development. The proposed driveways/parking lots across the project
will be privately maintained. The preliminary sections presented herein are for budgetary
estimating purposes only and are not for construction. The final pavement sections will be
provided after the fine grading operations are completed and, subgrade soils are sampled
and laboratory resistance value (R-Value) testing is performed on the soil samples
collected.
7.8.2 We calculated the flexible (asphalt concrete) and rigid (Portland cement) pavement
sections in accordance with State of California, Department of Transportation (Caltrans)
Highway Design Manual (Section 608.4) and procedure recommended by the American
Concrete Institute report AC! 330R-08 Guide for Design and Construction of Concrete
Parking Lots, respectively. In accordance with City of Carlsbad - Engineering Standards,
private parking lots and driveways shall be designed in accordance with City standards for
public streets. We used estimated Traffic Indices (TI) of 4.5 and 5.0 for design of the
private parking stalls and driveways. The project civil engineer and owner should review
the pavement designations to determine appropriate locations for pavement thickness.
7.8.3 A rigid Portland cement concrete (PCC) pavement section should be placed in driveway
entrance aprons and trash bin loading/storage areas. The concrete pad for the trash truck
areas should be large enough such that the truck wheels will be positioned on the concrete
during loading.
7.8.4 We used an estimated resistance value (R-Value) of 15 and 78 for subgrade soils and
aggregate base, respectively, in the flexible pavement calculations. We calculated the rigid
pavement section using the parameters presented on Table 7.8.1:
Project No. 07135-42-08 -20- September 1, 2015
TABLE 7.8.1
RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 100 pci
Modulus of rupture for concrete, MR 500 psi
Minimum Concrete Compressive Strength, f 3,200 psi
Traffic Category, TC A and C
Average daily truck traffic, ADTT 10 and 100
7.8.5 The preliminary recommendations for flexible and rigid pavement sections are presented
on Tables 7.8.2 and 7.8.3, respectively.
TABLE 7.8.2
PRELIMINARY FLEXIBLE PAVEMENT SECTIONS
Assumed Assumed Asphalt Class 2
Location Traffic Subgrade Concrete Aggregate
Index* R-Value (inches) Base (inches)
Private Parking Stalls 4.5 15 4.0 6.0
Private Driveways 5.0 15 4.0 6.0
*TI values are City of Carlsbad minimums and should be confirmed by the design team.
TABLE 7.8.3
PRELIMINARY RIGID PAVEMENT RECOMMENDATIONS
Location Portland Cement Concrete (inches)
Automobile Areas (TC=A, ADTT = 10) 5.5
Trash Truck Loading Area and Trash
.., Enclosures (TCC, ADTT =I 00)
* City of Carlsbad minimum.
7.8.6 Asphalt concrete should conform to Section 203-6 of the Standard Specifications for
Public Works Construction (Greenbook). Class 2 aggregate base materials should conform
to Section 26-1.02B of Caltrans or approved equivalent.
7.8.7 Prior to placing aggregate base materials or PCC slabs, the upper 12 inches of pavement
subgrade soils should be scarified, moisture conditioned as necessary, and compacted to a
dry density of at least 95 percent of the laboratory maximum dry density at to slightly
above optimum moisture content in accordance with ASTM D 1557. Base course material
Project No. 07135-42-08 -21 - September 1, 2015
should be moisture conditioned near to slightly above optimum moisture content and
compacted to a dry density of at least 95 percent of the laboratory maximum dry density.
7.8.8 Asphalt concrete pavement should be compacted to at least 95 percent of the laboratory
Hveem density in accordance with ASTM D 2726.
7.8.9 A thickened edge or integral curb should be constructed on the outside of concrete (PCC)
slabs subjected to wheel loads. The thickened edge should be 1.2 times the slab thickness
or a minimum thickness of two inches, whichever results in a thicker edge, at the slab edge
and taper back to the recommended slab thickness three feet behind the face of the slab
(e.g., a 7-inch-thick slab would have a 9-inch-thick edge).
7.8.10 Loading aprons such as trash bin enclosures and loading docks should utilize Portland
cement concrete as recommended in Table 7.8.3. The pavement should be reinforced with
No. 3 steel reinforcing bars spaced 24 inches on center in both directions placed at the slab
midpoint. The concrete should extend out from the trash bin such that both the front and
rear wheels of the trash truck will be located on reinforced concrete pavement when
loading.
7.8.11 To control the location and spread of concrete shrinkage cracks, crack-control joints
(weakened plane joints) should be included in the design of the concrete pavement slab.
Crack-control joints should not exceed 30 times the slab thickness with a maximum
spacing of 15 feet (e.g., a 7-inch-thick slab would have a 15-foot spacing pattern) and
should be sealed with an appropriate sealant to prevent the migration of water through the
control joint to the subgrade materials. The depth of the crack-control joints should be
determined by the referenced AC! report.
7.8.12 To provide load transfer between adjacent pavement slab sections, a butt-type construction
joint should be constructed. The butt-type joint should be thickened by at least 20 percent
at the edge and taper back at least four feet from the face of the slab. The project structural
engineer should be consulted to provide other alternative recommendations for load
transfer (i.e., dowels).
7.8.13 The performance of pavement is highly dependent on providing positive surface drainage
away from the edge of the pavement. Ponding of water on or adjacent to the pavement will
likely result in pavement distress and subgrade failure. Drainage from landscaped areas
should be directed to controlled drainage structures. Landscape areas adjacent to the edge
of asphalt pavements are not recommended due to the potential for surface or irrigation
water to infiltrate the underlying permeable aggregate base and cause distress. Where such
Project No. 07135-42-08 -22- September 1, 2015
a condition cannot be avoided, consideration should be given to incorporating measures
that will significantly reduce the potential for subsurface water migration into the aggregate
base. If planter islands are planned, the perimeter curb should extend at least six inches
below the level of the base materials.
7.9 Retaining Walls and Lateral Loads
7.9.1 Retaining walls not restrained at the top and having a level backfill surface should be
designed for an active soil pressure equivalent to the pressure exerted by a fluid density of
35 pounds per cubic foot (pcf). Where the backfill will be inclined at no steeper than 2.0 to
1.0, an active soil pressure of 50 pcf is recommended. These soil pressures assume that the
backfill materials within an area bounded by the wall and a 1:1 plane extending upward
from the base of the wall possess an Expansion Index of 50 or less. Selective grading may
be required to provide soil with an El of 50 or less for wall backfill. Geocon Incorporated
should be consulted for additional recommendations if backfill materials have an
Expansion Index greater than 50.
7.9.2 Where walls are restrained from movement at the top, an additional uniform pressure of 8H
psf (where H equals the height of the retaining wall portion of the wall in feet) 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 two feet of
fill soil should be added (soil total unit weight 130 pcf).
7.9.3 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
should be consulted to assess the suitability of the on-site soil for use as wall backfill if
standard wall designs will be used.
7.9.4 Unrestrained walls will move laterally when backfllled 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.
Project No. 07135-42-08 -23- September 1, 2015
7.9.5 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
(El 50) free-draining backfill material with no hydrostatic forces or imposed surcharge
load. A typical retaining wall drainage detail is presented on Figure 5. If conditions
different than those described are expected, or if specific drainage details are desired,
Geocon Incorporated should be contacted for additional recommendations.
7.9.6 In general, wall foundations having a minimum width and depth of one foot may be
designed for an allowable soil bearing pressure of 2,000 pounds per square foot (psf). The
allowable soil bearing pressure may 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 pressure of 3,500 psf. If high expansive soils are located at finish grade, the
wall footing should be extended at least 24 inches below low lowest adjacent grade. 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.
7.9.7 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 21H should be used for
design. We used the peak ground acceleration adjusted for Site Class effects, PGAM,
calculated from ASCE 7-10 Section 11. 8.3 and applied a pseudo-static coefficient of 0.33.
7.9.8 For resistance to lateral loads, a passive earth pressure equivalent to a fluid density of
300 pcf is recommended for footings or shear keys poured neat against properly compacted
granular fill soils or undisturbed formation materials. The passive pressure assumes a
horizontal surface extending away from the base of the wall at least five feet or three times
the surface generating the passive pressure, whichever is greater. The upper 12 inches of
material not protected by floor slabs or pavement should not be included in the design for
lateral resistance. Where walls are planned adjacent to and/or on descending slopes, a
passive pressure of 150 pcf should be used in design.
Project No. 0713542-08 -24- September 1, 2015
7.9.9 An allowable friction coefficient of 0.35 may be used for resistance to sliding between soil
and concrete. This friction coefficient may be combined with the passive earth pressure
when determining resistance to lateral loads.
7.9.10 The recommendations presented above are generally applicable to the design of rigid
concrete or masonry retaining walls having a maximum height of eight feet. In the event
that walls higher than eight feet or other types of walls (i.e., MSE walls) are planned,
Geocon Incorporated should be consulted for additional recommendations.
7.10 Slope Maintenance
7.10.1 Slopes that are steeper than 3:1 (horizontal:vertical) may, under conditions which are both
difficult to prevent and predict, be susceptible to near surface (surficial) slope instability.
The instability is typically limited to the outer three feet of a portion of the slope and
usually does not directly impact the improvements on the pad areas above or below the
slope. The occurrence of surficial instability is more prevalent on fill slopes and is
generally preceded by a period of heavy rainfall, excessive irrigation, or the migration of
subsurface seepage. The disturbance and/or loosening of the surficial soils, as might result
from root growth, soil expansion, or excavation for irrigation lines and slope planting, may
also be a significant contributing factor to surficial instability. It is, therefore, recom-
mended that, to the maximum extent practical: (a) disturbed/loosened surficial soils be
either removed or properly recompacted, (b) irrigation systems be periodically inspected
and maintained to eliminate leaks and excessive irrigation, and (c) surface drains on and
adjacent to slopes be periodically maintained to preclude ponding or erosion. It should be
noted that although the incorporation of the above recommendations should reduce the
potential for surficial slope instability, it will not eliminate the possibility, and, therefore, it
may be necessary to rebuild or repair a portion of the project's slopes in the future.
7.11 Low Impact Development (Bioswales, Permeable Pavement)
7.11.1 Bio-retention 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.
Project No. 07135-42-08 -25- September 1, 2015
7.11.2 The landscape architect should be consulted to provide the appropriate plant
recommendations for use with LID systems. If drought resistant plants are not used,
irrigation may be required
7.11.3 To minimize adverse impacts to existing or planned improvements, we recommend that the
LID systems be provided with a waterproof liner to prevent water infiltration and saturation
of the fill soils. This recommendation is intended to reduce potential negative impacts to
surface improvements due to water infiltration. Downstream properties may be subjected to
seeps, springs, slope instability, raised groundwater, movement of foundations and slabs, or
other impacts as a result of water infiltration. Saturating compacted fills typically results in
induced hydraulic settlement of the fills potentially impacting adjacent surface
improvements supported by the fill. Bioswale systems when located adjacent to pavements
often enable water to migrate beneath pavements saturating subgrade soils and aggregate
base, which can lead to premature pavement distress. Also, water may enter underground
utility pipe zones and impact improvements down gradient from the site.
7.11.4 As plans progress and construction details for LID systems are available for our review, we
can provide recommendations specific to LID systems planned for the site. Temporary
detention basins in areas where improvements have not been constructed do not need to be
lined.
7.12 Site Drainage and Moisture Protection
7.12.1 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.
7.12.2 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.
7.12.3 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
Project No. 07135-42-08 -26- September 1, 2015
movement could occur if water is allowed to infiltrate the soil for prolonged periods of
time.
7.12.4 Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. We
recommend that subdrains to collect excess irrigation water and transmit it to drainage
structures or impervious above-grade planter boxes be used. In addition, where landscaping
is planned adjacent to the pavement, we recommend construction of a cutoff wall along the
edge of the pavement that extends at least six inches below the bottom of the base material.
7.13 Precise Grading and Foundation Plan Review
7.13.1 Geocon Incorporated should review the precise grading and foundation plans prior to final
City submittal/approval to check their compliance with the recommendations of this report
and to determine the need for additional comments, recommendations and/or analysis.
Project No. 07135-42-08 -27- September 1, 2015
LIMITATIONS AND UNIFORMITY OF CONDITIONS
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.
The recommendations of this report pertain only to the site investigated and are based upon
the assumption that the soil conditions do not deviate from those disclosed in the
investigation. If any variations or undesirable conditions are encountered during construction,
or if the proposed construction will differ from that anticipated herein, Geocon Incorporated
should be notified so that supplemental recommendations can be given. The evaluation or
identification of the potential presence of hazardous or corrosive materials was not part of the
scope of services provided by Geocon Incorporated.
This report is issued with the understanding that it is the responsibility of the owner or his
representative to ensure that the information and recommendations contained herein are
brought to the attention of the architect and engineer for the project and incorporated into the
plans, and the necessary steps are taken to see that the contractor and subcontractors carry out
such recommendations in the field.
The findings of this report are valid as of the present date. However, changes in the
conditions of a property can occur with the passage of time, whether they be due to natural
processes or the works of man on this or adjacent properties. In addition, changes in
applicable or appropriate standards may occur, whether they result from legislation or the
broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly
or partially by changes outside our control. Therefore, this report is subject to review and
should not be relied upon after a period of three years.
Project No. 07135-42-08 September 1, 2015
I
N
NO SCALE
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 CLIENTS 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
INCORPORATED
GEOTECHNICALU ENVIRONMENTAL U MATERIALS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974
PHONE 858 558-6900 - FAX 858 558-6159
RM I AML DSKIGTYPD
QUARRY CREEK PA R-1
CARLSBAD, CALIFORNIA
DATE 09-01-2015 1 PROJECT NO. 07135 - 42 - 08 1 FIG. 1
P4tod:09/01)2015 3:41 PM I BykLVIN LADRJLEONO I FNo Lo oIIro:Y:\PROJECTSO7135-42.O8 00003 Crook- RI)\0€T4JLS7135-42.08Vk Mop.4w9
APPENDIX
APPENDIX A
RECOMMENDED GRADING SPECIFICATIONS
FOR
QUARRY CREEK PLANNING AREA R-1
CARLSBAD, CALIFORNIA
PROJECT NO. 07135-42-08
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 Geotechnical Report are a part of the earthwork and grading specifications
and shall supersede the provisions contained hereinafter in the case of conflict.
1.2 Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for
substantial conformance with the recommendations of the Geotechnical Report and these
specifications. The Consultant should provide adequate testing and observation services so
that they may assess whether, in their opinion, the work was performed in substantial
conformance with these specifications. It shall be the responsibility of the Contractor to
assist the Consultant and keep them apprised of work schedules and changes so that
personnel may be scheduled accordingly.
1.3 It shall be the sole responsibility of the Contractor to provide adequate equipment and
methods to accomplish the work in accordance with applicable grading codes or agency
ordinances, these specifications and the approved grading plans. If, in the opinion of the
Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture
condition, inadequate compaction, 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.
GI rev. 07/2015
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 % inch in size.
3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than
4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than
12 inches.
3.1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than 3/4 inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
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
GI rev. 07/2015
and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall
not be responsible for the identification or analysis of the potential presence of hazardous
materials. However, if observations, odors or soil discoloration cause Consultant to suspect
the presence of hazardous materials, the Consultant may request from the Owner the
termination of grading operations within the affected area. Prior to resuming grading
operations, the Owner shall provide a written report to the Consultant indicating that the
suspected materials are not hazardous as defined by applicable laws and regulations.
3.4 The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of
properly compacted soil fill materials approved by the Consultant. Rock fill may extend to
the slope face, provided that the slope is not steeper than 2:1 (honzontal: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 11/2 inches in diameter shall be removed to a depth of 3 feet
below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to
provide suitable fill materials.
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 (3eotechnical 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 Ground
Finish Slope Surface
Remove All - ' - Unsuitable Material
As Recommended By Slope T7BeSuch That Consultant Sloughing Or Sliding
Does Not Occur I
See Note 1 See Note 2
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 surflcial 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.
GI rev. 07/2015
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
Glrev. 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
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.
Ci! 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 10-Pound
Hammer and 18-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.
G1 rev. 07/2015
LIST OF REFERENCES
Boore, D. M., and G. M Atkinson (2006), 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.
California Geological Survey, Seismic Shaking Hazards in California,Based on the USGS/CGS
Probabilistic Seismic Hazards Assessment (PSHA) Model, 2002 (revised April 2003). 10%
probability of being exceeded in 50 years.
(http://redirect.conservation.ca.gov/cgs/rghm/pshamap/pshamain.html).
Campbell, K. W., and Y. Bozorgnia, NGA Ground Motion Model for the Geometric Mean
Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response
Spectra for Periods Ranging from 0.01 to 10 s, Preprint of version submitted for publication
in the NGA Special Volume of Earthquake Spectra. Volume 24, Issue 1, pages 139-171,
February 2008.
Risk Engineering, EZ-FRISK (version 7.65).
USGS computer program, Seismic Hazard Curves and Uniform Hazard Response Spectra
(version 5.1.0, dated February 2, 2011), http://earthquake.usgs.gov/research/hazmaps/design/.
Kennedy, M. P. and S. S. Tan, 2005, Geologic Map of the Oceanside 30 'x60' Quadrangle,
California, USGS Regional Map Series Map No. 2, Scale 1:100,000.
Unpublished reports, aerial photographs, and maps on file with Geocon Incorporated.
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).
Project No. 07135-42-08 September 1, 2015