HomeMy WebLinkAboutCT 13-03; ROBERTSON RANCH-RANCHO COSTERA; GEOTECHNICAL RECOMMENDATIONS REPORT; 2014-11-04LGC Valley, Inc.
Geotechnical Consulting
RECEIVED
NOV07 2014.
LANIJ LJVCLUtJjLIEN
GEOTECliNICAL RECOMMENDATIONS REPORT
FOR THE PLANNED IMPROVEMENTS OF
EL CAMINO REAL, BETWEEN
CANNON ROAD AND TAMARACKA VENUE,
CARLSBAD, CALIFORNIA
O—'
Dated: November 4, 2014
Project No. 133023-05
Prepared For:
Toll Brothers, Inc.
725 W. Town & Country Road, Suite 200
Orange, California 92868
2420 Grand Ave, Suite F-2, Vista - CA 92081 • (760) 599-7000 • Fax (760) 599-7007
LGC Valley, Inc.
Geotechnical Consulting
November 4, 2014
Mr. Kevin Brickley
Toll Brothers Inc.
725 W. Town & Country Road, Suite 200
Orange, California 92868
Project No. 133023-05
Subject: Geotechnical Recommendations Report for the Improvement of El Camino Real between
Cannon Road and Tamarack Avenue, Carlsbad, California
In accordance with your request, LGC Valley, Inc. (LGC) has performed a geotechnical evaluation of the
proposed improvement along El Camino Real between Cannon Road (Station No. 444+00) and Tamarack
Avenue (Station No. 494+00) in Carlsbad, California. The purpose of our study was to evaluate the existing
onsite geotechnical conditions relative to the current grading/improvement plan design and to provide
geotechnical recommendations applicable to the planned roadway, median, and parkway improvements for the
project. Our study included a review of the previous geotéchnical documents of the site by GeoSoils; review of
available pertinent geotechnical and geologic reports and maps relative to the general vicinity; an aerial
photographic review of the site, a site reconnaissance; analysis of the collected data; and preparation of our
findings, conclusions, and recommendations relative to the proposed El Camino Real improvements.
Based on our evaluation, it is our professional opinion that the site design is suitable from a geotechnical
perspective provided the findings, conclusions, opinions, and recommendations contained within this report are
implemented during site development.
If you have any questions regarding our report, please contact this office. We appreciate this opportunity to
be of service.
Respectfully submitted,
LGC VALLEY, INC
aa &w Randall agne,CEG1
Senior Project Geologist
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CERTIFIED ' I ENGINEERING I * ' GEOLOGIST I * " (-~K-
Basil Hattar, GE 2734
Principal Engineer
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LU No. 2734
Exp. 6/30/16
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Distribution: (6) Addressee
2420 Grand Ave, Suite F-2, Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007
TABLE OF CONTENTS
Section
1.0 INTRODUCTION
1.1 ......PURPOSE AND SCOPE OF SERVICES .............................................................................................I
1.2......SITE AND PROJECT DESCRIPTION ................................................................................................1
1.3......PREVIOUS GEOTECHNICAL WORK ............................................................................................... 2
2.0 GEOTECHI'4ICAL CONDITIONS..............................................................................................4
2.1 ......REGIONAL GEOLOGY..................................................................................................................4
2.2 ...... SITE-SPECIFIC GEOLOGY ............................................................................................................4
2.3......GEOLOGIC STRUCTURE..............................................................................................................5
2.4......GROUND AND SURFACE WATER.................................................................................................6
2.5......SLOPE STABILITY ....................................................................................................................... 6
2.6......ENGINEERING CHARACTERISTICS OF THE ON-SITE SOILS...........................................................7
3.0 CONCLUSIONS............................................................................................................................8
4.0 RECOACKENDATIONS ............................................................................................................. 10
4.1......SITE EARTHWORK .................................................................................................................... 10
4.1.1... Site Preparation...........................................................................................................10
4.1.2... Removal and Recompaction.......................................................................................10
4.1.3... Shrinkage/Bulking ...................................................................................................... 11
4.1.4... Temporary Stability of Removal Excavations ............................................................ ii
4.1.5 ... Fill Placement and Compaction..................................................................................12
4.1.6... Trench Backfill and Compaction................................................................................12
4.2 ...... PAVEMENT RECOMMENDATIONS ..............................................................................................13
4.2.1 ... Existing Pavement......................................................................................................13
4.2.2... New Pavement Areas..................................................................................................13
4.3......RETAINING WALLS 14
4.3.1 ... Lateral Earth Pressures and Retaining Wall Design Considerations..........................14
4.3.2 ... Freestanding (Top-of-Slope) Walls ............................................................................16
4.4 ...... CORROSIVITY TO CONCRETE AND METAL.................................................................................16
4.5 ...... CURB AND GUTTER AND SIDEWALK RECOMMENDATIONS ........................................................17
4.4......CONTROL OF SURFACE WATER AND DRAINAGE CONTROL .......................................................17
4.5......PLAN REVIEW, CONSTRUCTION OBSERVATION AND TESTING...................................................17
5.0 L11'11'1'&'IIONS ............................................................................................................................ 18
Project No. 133023-05 Page i November 4, 2014
LIST OF TABLES, APPENDICES AND ILLUSTRATIONS
Plates
Plate 1 - Geotechnical Map (In Pocket)
Figures
Figure 1 - Retaining Wall Detail, Sand Backfill (Rear of Text)
Figure 2 - Geotechnical Parameters for Top of Slope Walls (Rear of Text)
ADvendices
Appendix A - References
Appendix B - General Earthwork and Grading Specifications for Rough Grading
Project No. 133023-05 Page ii November 4, 2014
1.0 INTRODUCTION
1.1 Purpose and Scope of Services
The main purpose of this study was to evaluate the proposed improvements along El Camino Real
between Cannon Road (Station No. 444+00) and Tamarack Avenue (Station No. 494+00) from a
geotechnical perspective and to provide preliminary geotechnical recommendations relative to the
grading and improvement operations along the roadway. This report was prepared to summarize the
existing geotechnical conditions and changes to the site since the previous geotechnical investigations
were performed, and to provide our geotechnical findings, conclusions, opinions, and recommendations
relative to the grading of the roadway. Our scope of services included:
Review the civil drawings and the latest grading plans prepared by O'Day Consultants (Appendix
A), which was used as a base for our geotechnical map (Plate 1).
Review of pertinent available geotechnical literature/publications, geologic maps, and aerial
photographs (Appendix A).
Review of previous geotechnical reports prepared by GeoSoils, Inc. pertinent to the proposed
roadway development. The reports are listed in Appendix A.
Reconnaissance and geologic mapping of the site.
Geotechnical analysis of the data accumulated during our study.
Preparation of this report presenting our findings, conclusions, interpretations, and
recommendations including the General Earthwork and Grading Specifications for Rough Grading
(Appendix B) with respect to the proposed rough and post grading of the roadway.
1.2 Site and Project Description
The proposed project consists of the roadway, median, and parkway improvements along the north
and south sides of a portion of El Camino Real (ECR) from the intersection of Cannon Road (at
approximate Station 444+00) to Tamarack Avenue (at approximate Stations 494+00).
ECR currently consists of two travel lanes and a bike lane in each direction and a center median
delineated by double yellow lines. In addition to the Cannon Road and Tamarack Avenue
intersections, there are a total of three other intersections (Crestview Drive, Lisa Street and Kelly
Drive) along the south side of the street. Numerous utility lines are present along and crossing the
street. Site elevations range from a high of approximately 85 feet mean sea level (msl) in the vicinity
of Station 462+00 to a low of approximately 41 feet msl near Station 446+00.
Project No. 133023-03 Page 1 November 4, 2014
Proposed improvements include:
Widening the entire north side of the street to create an additional lane and widening portions of
the south side that have not previously been widened in order to create an additional lane by
placing fill;
Re-grading the relatively-steep existing slope to slope inclinations of 2:1 (horizontal to vertical)
or flatter and construction of a top of slope wall and a retaining wall on the south side between
Stations 459+50 and 462+50;
Construction of 11 bioretention areas;
Placement of a center median along the street with planter areas and pervious pavement;
Construction of two bus turn-outs;
Placement of new asphalt concrete (AC) and rehabilitation of existing AC by grinding and the
addition of a two inch overlay;
Installation of concrete sidewalk along the entire north side of the street and on the south side of
the street between Stations 454+75 to 462+50 and 469+50 to 483+75;
Construction/extension of two storm drain culverts;
Installation of approximately 6,200 linear feet (If) of storm drain, 550 If of sewer line, 5,200 If of
water line, and 7,300 If of subdrains.
1.3 Previous Geofechnicai Work
The findings, conclusions and recommendations presented in this report are based on our review of
current grading plans, understanding of the project and review of previous work completed by GeoSoils
for the adjacent Robertson Ranch project and a site specific investigation for the El Camino Real
roadway improvements (Appendix A).
As a part of the previous geotechnical work performed by GeoSoils for El Camino Real, an evaluation
of the existing pavement section was performed within the proposed subject area. Based on our review
of the previous work, the following is a summary of the previous pavement section evaluation
(GeoSoils, 201 la):
The existing as-built pavement sections, at previous investigation locations, along El Camino Real
were measured and the existing pavement distress was observed and documented.
The existing pavement generally consists of a 6- to 8-inch thick layer of asphaltic concrete (AC),
underlain by an approximately 4-inch thick layer of what appears to be a recycled asphalt pavement
(RAP). The AC/RAP section was then observed to be underlain by a 12- to 18-inch layer of silty
sand (select fill or sub base), overlying clayey subgrade soils. The previous report by GeoSoils
indicates that a subgrade sample was collected at the exploration locations for R-value testing. R-
value testing along El Camino Real resulted in a range of R-values from 8 to 31, with the majority
of the results being in the 14 to 16 range.
Based on the previous evaluation (by others), the most prevalent type of pavement distress along
ECR appeared to be fatigue/alligator cracking. Based on the Asphalt Institute, fatigue cracking
consists of a series of interconnected cracks caused by fatigue failure of the asphalt surface under
repeated, excessive traffic loads, due to: 1) poor drainage, or 2) a weak base or subgrade layer.
Project No. 133023-05 Page 2 November 4, 2014
Previous observations (by GeoSoils) indicated that moderate fatigue cracks occur within the wheel
paths within the slow lane, and/or the previous location of the slow lane prior to median
construction between Stations 444+00 and 455+00. From Stations 455+00 to 459+00, fatigue
cracking appears within the wheel path nearest the bike lane, and along the approximate location of
an approximately 6-inch wide utility trench patch. Moderate fatigue cracking was observed within
the wheel path, located just outside the bike lane from approximate Stations 464+50 to 469+50, and
in the vicinity of the 6-inch wide utility trench patch. Light, localized fatigue cracking was
observed, primarily within the slow lane, from Stations 476+50 through Station 478+50. From
Stations 486+50 to 491 +50, light to moderate fatigue cracking was noted with the slow lane, with
light cracking also observed within the fast lane. Based on (ieoSoils review, a greater degree of
fatigue cracking appears to coincide with pavement areas underlain with alluvial soils and a
relatively shallow groundwater table. Other areas of fatigue cracking may also be associated with
poor drainage along the margins of the roadway, especially in the vicinity of Stations 476+50 to
478+50.
Patching (or areas of pavement that has been replaced with new AC to repair the existing
pavement), was observed throughout the roadway. A patch to repair existing pavement is
considered a defect, and temporary, no matter how well it performs.
Localized depressions, or ruts were noted within the wheel path nearest the center median in the
vicinity of Station 461 +00, and between Stations 486+50 to 491 +50. Potholes also appear to be
forming within these areas.
Minor areas of polished aggregate, raveling, etc. were noted locally and are likely an indication of
pavement age. Areas of water seepage or ponding were not observed along the roadway.
Project No. 133023-05 Page 3 November 4, 2014
2.0 GEOTECHNICAL CONDITIONS
2.1 Regional Geology
The subject site is located within the coastal subprovince of the Peninsular Ranges Geomorphic
Province, near the western edge of the southern California batholith. The topography at the edge of
the batholith changes from the rugged landforms developed on the batholith to the more subdued
landforms which typify the softer sedimentary formations of the coastal plain such as those present
on the site.
Specifically, the area is underlain mainly by sedimentary units of the' Tertiary-aged Santiago
Formation. Subsequent to the deposition of this unit, erosion and regional tectonic uplift created
the valleys and ridges of the area. Recent weathering and erosional processes have produced the
Quaternary terrace/older alluvial flood-plain deposits, younger alluvium and colluvium while
human influences have created the mapped and unmapped documented and undocumented fill
soils that mantle the site.
2.2 Site-SDecific Geolog y
Based on our review of the available previous geotechnical reports for the El Camino Real alignment
and pertinent geologic literature and maps of the vicinity, the primary bedrock unit along the
roadway is sandstone of the Tertiary-aged Santiago Formation. The Santiago Formation is overlain
by Quatemary-aged terrace/older alluvial flood-plain deposits, alluvium, surficial deposits and recent
artificial fills. The approximate extent of these geologic units present along the roadway are depicted
on the Geotechnical Map (Plate 1) and discussed below youngest to oldest.
Artificial Fill: Existing artificial fills were previously encountered (by others) within the alignment of
El Camino Real that were placed during previous grading operations for construction of El Camino
Real. Existing roadway fill soils were previously encountered primarily along El Camino Real
between approximately Stations 444+00 to 453+00, 464+00 to 471+00, and 481+50 to 488+50.
These fill soils; designated as Af, generally consist of clayey to silty sands and sandy clays and are
anticipated to be on the order of less than 5 to 15 feet in thickness. If encountered during future
grading, remedial measures (such as removal and recompaction, where practical) should be
anticipated. The approximate limits of these fill soils are presented on Plate 1.
Surficial Deposits: Surficial deposits were observed along the base of the relatively steep cut slopes
along the roadway alignment. Theses deposits are loose soils that have been deposited at the base of
the slopes in response to gravity and should be completely removed as part of the grading operations
prior to the construction of the roadway improvements. It is anticipated that these soils are I to 3 feet
in thickness.
Project No. 133023-05 Page 4 November 4, 2014
I
Ouatemary Alluvium: Alluvium soils were previously encountered (by others) along El Camino
Real, where buried drainages crossed the roadway. These deposits typically consist of light brown to
brown sands, sandy clays and clayey sands that are low to highly expansive, porous, and contain
scattered organics. As encountered, the alluvium is considered potentially compressible with
potentially liquefiable layers below the existing groundwater level. The alluvial soils are anticipated
to be encountered along the roadway between approximately Stations 444+00 to 452+00, 465+00 to
468+00, 481+00 to 484+50, and 486+00 to 487+50. In general, the alluvium is estimated to be 4 to
20+ feet in thickness. Where encountered, the alluvium should be removed to competent formational
material, to within a few feet or the groundwater table, or to a depth of approximately 5 feet. Where
removals are not practical due to existing buried utility lines or remedial removals to a depth of 5 feet
does not reach competent soils, placement of a stabilization geotextile will be required.
Ouatemary Terrace Deposits: Quatemary-aged terrace or older alluvial flood-plain deposits (as
mapped by Kennedy & Tan, 2005) were previously encountered (by others) along the roadway
between approximate Stations 452+00 and 464+00. These soils consist of silty sand to sandy-silty
clay that are considered mid-to late-Pleistocene in age. The weathered portion of this unit is
considered potentially compressible and is anticipated to be on the order of I to 3 feet in thickness.
The expansion potential of these soils range from very low to highly expansive.
Santiago Formation: The Tertiary-aged Santiago Formation, which was previously observed (by
others) and was observed during our site observations, consists primarily of massively bedded to
cross-bedded silty sandstones and minor clayey sandstones and claystoneslsiltstones. The siltstones
and claystones generally are olive green and red brown to olive gray (unweathered), damp to moist,
stiff to hard, moderately fractured and sheared. The sandstone generally consists of light olive green,
olive green, light brown and pale orange brown (where iron-oxidized stained), damp to moist, dense
to very dense, silty very fine to medium grained sandstone. The Santiago Formation was previously
encountered (by others) at grade along the roadway between approximately Stations 471+00 to
48 1+00 and at depth along the remainder of the roadway.
2.3 Geologic Structure
The overall structure of the bedrock on the site is dipping slightly to the south/southwest with dips less
than 18 to 24 degrees. Based on the subsurface data, bedding within the Santiago Formation is thin to
thickly bedded and generally exhibits variable bedding with strikes ranging from northwest to northeast
and dips typically 4 to 16 degrees to the south, southwest, and to a lesser extent to the northeast.
Locally, cross bedding was observed with dips ranging from 15 to 28 degrees. Clay seams encountered
in the previous borings (by others) generally trend parallel to the bedding. Bedding observed within the
terrace deposits in test pits (by others), and exposed in road cuts along El Camino Real, display
generally massive to thickly bedded sediments, and poorly developed sub-horizontal orientation.
Jointing on-site is variable, but predominantly trends north to northwest, and to a lesser extent to the
northeast. Jointing dips were found to be generally moderately to steeply dipping (dips on the order of
45 to 89 degrees). Jointing was mainly encountered in the upper portion of the bedrock becoming less
pronounced with depth.
Project No. 133023-05 Page 5 November 4, 2014
Randomly oriented shears were encountered in the Santiago Formation claystone and siltstone.
Numerous wide, diffuse zones of shearing, as well as more well-defined zones, were encountered in the
bedrock, and are thought to be the result of regional tectonic uplifting imparting shearing forces to the
relatively stiff and unyielding siltstone and claystone.
2.4 Ground and Surface Water
Groundwater was encountered in some of the borings completed during the previous site investigation
by GeoSoils in two distinct areas along the El Camino Real roadway; one in the general vicinity of
Cannon Road between approximate Stations 444+00 to 452+00; the other between approximately
Stations 481+50 and 488+00 in the vicinity of Kelly Drive. Groundwater was encountered at an
approximate elevation ranging from 8 to 21 feet below the existing roadway, or at an approximate
elevation of 32 to 34 feet (msl) between Stations 444+00 to 452+00; while the groundwater elevation
was encountered at depths ranging from 5 to 16 feet below the existing roadway grade, or at an
approximate elevation of 42 to 43 feet (msl) between Stations 481+50 and 488+00.
Within these areas of shallow groundwater, trenching for the deeper utility improvements within the
roadway, as well as any planned grading along the margins of the roadway in these areas, will likely
encountered a shallow groundwater elevation. For planning purposes, dewatering during trenching
operations should be anticipated, especially where excavations deeper than about 5 feet occur in close
proximity to the anticipated shallow groundwater elevations. Regional groundwater should not
adversely affect site development provided that the recommendations presented in this report are
properly incorporated into the design and construction of the project. We recommend that periodic
inspection be made by our engineer or geologist during the grading operations and/or construction for
the presence of groundwater. Remedial measures, if any, can be recommended on a case-by-case basis
during the grading and construction operations.
2.5 SloDe Stability
Our review of the grading plans for the El Camino Real roadway improvements (O'Day, 2014)
indicates that the proposed cut and fill slopes along the southern side of the roadway are proposed at
a maximum inclination of 2:1 (horizontal to vertical) and up to approximately 20 and 5 feet in height,
respectively. Cut slopes along the southern side of the roadway are anticipated to be cut into
competent terrace deposits, and remedial removals are recommended underlying proposed fill slopes
such that the minor fill slopes will be placed/keyed into competent fills. It should be noted that the
design slopes along the northern side of El Camino Real were previously reviewed and are being
graded as part of the adjacent Robertson Ranch development; and therefore, are not part of this
project. The previous slope stability analysis indicated that the proposed cut and fill slopes have are
considered globally and surficially stable and have global factors of safety of at least 1.5 and 1.1 for
static and seismic conditions, respectively.
Project No. 133023-05 Page 6 November 4, 2014
Z6 En2ineerin2 Charaderistia of the On-Site Soils
Based on our review of the laboratory test results from the previous site investigations (by GeoSoils)
of representative on-site soils and our professional experience on adjacent sites with similar soils, the
engineering characteristics of the on-site soils are discussed below.
Resistance Value: Resistance Value (i.e. R-Value) testing of representative soils samples during the
previously roadway geotechnical investigation by GeoSoils indicates the roadway soils possess R-
Values ranging from 8 to 31 (with the majority of the test results in the 14 to 16 range).
Corrosivity Testing: Based on the limited corrosivity testing by GeoSoils of representative soils
relative to the adjacent Robertson Ranch project, the tested soils have a pH ranging from 6.6 to 8.4;
a sulfate content of 30 to 560 parts per million (ppm); chloride content of 100 to 910 ppm, and a
minimum resistivity of 240 to 1,100 (ohms-cm). Caltrans currently considers a site to be corrosive to
foundation elements if one or more of the following conditions exist: chloride concentrations are
greater than or equal to 500 ppm, sulfate concentrations are greater than or equal to 2000 ppm or the
pH is 5.5 or less. Based on the initial test results by GeoSoils, the site soils have negligible soluble
sulfates and are considered corrosive per Caltrans criteria.
Excavation Characteristics: The roadway is underlain by silty to clayey sand to sandy clay surficial
units and formational silty to clayey sandstones and siltstones/claystones. It is anticipated that the on-
site materials can be excavated with conventional heavy-duty construction equipment. Difficult
excavation may be encountered where cemented layers are encountered within the Santiago
Formation.
Project No. 133023-05 Page 7 November 4, 2014
3.0 CONCLUSIONS
Based on the results of our geotechnical evaluation at the subject site and our review of the previous geotechnical
reports applicable to the El Camino Real roadway, it is our professional opinion that the proposed rough and post
grading of El Camino Real between Cannon Road (Station No. 444+00) and Tamarack Avenue (Station No.
494+00) is feasible from a geotechnical standpoint, provided the following conclusions and recommendations are
incorporated into the project plans, specifications, and followed during the site grading operations. The following is
a summary of the geotechnical conclusions derived from our study:
The proposed site area is underlain by the Santiago Formation, terrace deposits, alluvium, surficial deposits and
existing artificial fill soils.
The undocumented fill, surficial deposits, upper portion of the alluvium, and weathered formational materials
are considered unsuitable in their present state and will require removal and recompaction in areas of proposed
street improvements or future fills.
Based on previous subsurface exploration (by LGC and GeoSoils) and our field geologic mapping, the
generalized site bedrock is dipping up to 18 to 24 degrees to the south and southwest and as such is generally a
non-favorable (i.e. out-of-slope) orientation for design slopes which face south. However, proposed south facing
slopes with exposed bedrock along the north side of El Camino Real are designed to be removed and replaced
with a fill slope with a design key with Verdura Walls. These slopes were evaluated and are being constructed as
a part of grading for the adjacent residential development.
The existing on-site soils appear to be suitable material for use as fill provided they are relatively free of rocks
(larger than 8 inches in maximum dimension), organic material and debris.
Active faults are not known to exist on or in the immediate vicinity of the site. Because of the lack of known
active faults on the site, the potential for surface rupture at the site is considered very low.
The main seismic hazard that may affect the site is ground shaking from one of the active regional faults.
Based on the previous site evaluations (by others), relatively shallow groundwater and loose sandy alluvial
soils were encountered where buried drainages cross the roadway. The potential for liquefaction of these
alluvial soils is considered moderate unless provisions to mitigate the potential liquefaction (i.e. remedial
removals or subgrade modification) are performed during site grading.
During the previous geotechnical investigation of the roadway by GeoSoils, shallow groundwater was
encountered between Stations 444+00 to 452+00 at a depth of 8 to 21 feet below existing grades and between
Stations 481+50 to 488+00 at a depth of 5 to 16 feet below existing grades. Utility trenches deeper than 5 to 8
feet in these areas will likely encounter groundwater conditions that will need to be mitigated. If groundwater
seepage conditions are encountered during site development, recommendations to mitigate the conditions can be
made on a case-by-case basis at that time.
Based on resistance testing of representative soils along the roadway during the previous site investigation, R-
Values ranging between 8 and 31 were obtained; however, the majority of the test results ranged between 14 and
16.
Project No. 133023-05 Page 8 November 4, 2014
Based on limited laboratory testing and our professional experience on adjacent sites, the on-site soils have a
low to high expansion potential, possess a negligible soluble sulfate content, and are considered corrosive per
Caltrans criteria. However, some of the soils may possess a moderate to high sulfate content and may be very
corrosive; therefore, corrosion testing should be performed at the completion of grading to assess this
potential, as necessary.
With the exception of localized cemented zones within the Santiago Formation, it is anticipated that the on-
site sedimentary and surficial soils can be excavated with conventional heavy-duty construction equipment.
Localized cemented zones may require heavy ripping.
All oversized material (if encountered) should be placed in accordance with the recommendations presented in
Appendix B to minimize settlement of the material around the oversized rocks.
Project No. 133023-05 Page 9 November 4, 2014
4.0 RECOMMENDATIONS
4.1 Site Earthwork
We anticipate that earthwork at the site will consist of site preparation and remedial grading followed
by subgrade preparation for the proposed roadway widening, cut and fills for design slopes,
construction of site walls, construction of bio-retention areas, construction of curb and gutters,
aggregate base and asphaltic concrete placement, and sidewalk construction. We recommend that
earthwork and construction onsite be performed in accordance with the following recommendations,
and the City of Carlsbad requirements.
4.1.1 Site Preparation
Prior to grading of areas to receive structural fill or pavement areas, the areas should be
cleared of surface obstructions, any existing debris, potentially compressible material (such as
undocumented or unsuitable fill soils, unsuitable alluvium, or weathered bedrock) and stripped
of vegetation. Vegetation and debris should be removed and properly disposed of offsite.
Holes resulting from the removal of buried obstructions or utilities, should be replaced with
suitable compacted fill material. Areas to receive fill and/or other surface improvements
should be scarified to a minimum depth of 6 inches, brought to a near-optimum moisture
condition, and recompacted to at least 90 percent relative compaction (based on American
Standard of Testing and Materials [ASTM] Test Method D1557).
4.1.2 Removal and Reconwaclion
As discussed in Section 2.2, the upper portion of the site is underlain by potentially
compressible unsuitable soils (existing undocumented fills, alluvium, and weathered terrace
and bedrock material), which may settle under the surcharge of fill and/or traffic loads.
Compressible materials not removed by the planned grading should be excavated to competent
material and replaced with compacted fill soils.
We anticipate removals on the site underlying proposed new roadway areas, proposed fill areas,
and proposed slopes, will be on the order of 3 to 5 feet below existing grade (as shown on Plate
1); however, localized, deeper removals should be anticipated (where deemed necessary by the
geotechnical consultant based on observations during grading).
Anticipated removals within existing fills, upper terrace deposits, and weathered bedrock are
anticipated to be on the order of 2 to 3 feet below existing grade. Where encountered, the
alluvial soils should be removed either to competent alluvium, terrace deposits, or bedrock, to
within a few feet or the groundwater table, or to a maximum depth of approximately 5 feet.
Where removals are: 1) not practical due to existing buried utility lines or other conditions; 2)
remedial removals to a depth of 5 feet do not reach competent soils; or 3) wet saturated soils
are encountered at removal bottoms, placement of a stabilization geotextile (Mirafi HP 570 or
equivalent) and rock (as necessary for wet/saturated bottoms) will be required. Based on the
Project No. 133023-05 Page 10 November 4, 2014
thickness of existing alluvium, it should be anticipated that a stabilization geotextile will need
to be placed in the majority of the areas with underlying alluvium.
If wet/saturated removal bottoms are encountered, construction of a rock blanket consisting of
crushed rock (generally 3- to 6-inch minus) overlying the stabilization geotextile is
recommended to create a suitable bottom and will be necessary to allow for fill placement
above. The thickness of the rock blanket should be determined based on the actual conditions
encountered; and is, therefore, not provided herein. Wet conditions should be observed and
evaluated on a case-by-case basis by the project geologist/engineer as other conditions and
options may apply.
From a geotechnical perspective, material that is removed may be placed as fill provided the
material is relatively free from rocks (greater than 8 inches in maximum dimension), organic
material and construction debris, is moisture-conditioned or dried (as needed) to obtain above-
optimum moisture content, and then recompacted prior to additional fill placement or
construction.
4.1.3 Shrinkage/Bulking
The volume change of excavated on-site materials upon recompaction as fill is expected to
vary with materials and location. Typically, the surficial soils and bedrock materials vary
significantly in natural and compacted density, and therefore, accurate earthwork
- shrinkage/bulking estimate cannot be determined. However, the following factors (based on
the results of our previous subsurface investigation and previous investigations by GeoSoils
[Appendix A]), laboratory testing, geotechnical analysis and professional experience on
adjacent sites) are provided on the following table as guideline estimates.
Earthwork Shrinkage and Bulking Estimates
Geologic Unit Estimated Shrinkage/Bulking
Existing Artificial Fills 5 to 10 percent shrinkage
Alluvium 10 to 15 percent shrinkage
Terrace Deposits 5 percent shrinkage to 3 percent bulking
Santiago Formation 3 to 7 percent bulking
4.1.4 Temporary Stability of Removal Excavations
Due to the recommended depth of remedial grading (ranging from 2 to 5 feet), the temporary
stability of the excavations along the perimeter of the site should be within tolerable range.
However if earthwork depths exceed anticipated values, temporary stability needs to be
considered. All excavations for the proposed development should be performed in accordance
with current OSHA (Occupational Safety and Health Agency) regulations and those of other
regulatory agencies, as appropriate.
Temporary excavations maybe cut vertically up to five feet. Excavations over five feet should
be slot-cut, shored, or cut to a 1H:IV (horizontal, H: vertical, V) slope gradient. Surface water
Project No. 133023-05 Page 11 . November 4, 2014
should be diverted away from the exposed cut, and not be allowed to pond on top of the
excavations. Temporary cuts should not be left open for an extended period of time. Planned
temporary conditions should be reviewed by the geotechnical consultant of record in order to
reduce the potential for sidewall failure. Based on actual conditions, the geotechnical
consultant may provide addendum recommendations for controlling the length of sidewall
exposed.
4.1.5 Fill Placement and Compaction
From a geotechnical perspective, the onsite soils are generally suitable for use as compacted
fill, provided they are screened of rocks greater than 8 inches in maximum dimension, organic
materials and construction debris. Areas prepared to receive structural fill and/or other surface
improvements should be scarified to a minimum depth of 6 inches, brought to at Least
optimum-moisture content, and recompacted to at least 90 percent relative compaction (based
on ASTM Test Method D1557). The upper one foot of subgrade soils below concrete and
pavement section should be compacted to at least 95 percent relative compaction. The optimum
lift thickness to produce a uniformly compacted fill will depend on the type and size of
compaction equipment used. In general, fill should be placed in uniform lifts generally not
exceeding 8 inches in compacted thickness. Placement and compaction of fill should be
performed in accordance with local grading ordinances under the observation and testing of the
geotechnical consultant.
In general, oversized material shall not be placed within the street section, but may be placed
below this zone if oversized material is broken down to a maximum of 8 inches in diameter and
incorporated into the fill.
If possible, import soils should contain no materials over 8 inches in maximum dimension and
have a low expansion potential.
4.1.6 Trench Backfill and Compaction
The onsite soils may generally be suitable as trench backfill provided they are screened of rocks
and other material over 6 inches in diameter and organic matter. Trench backfill should be
compacted in uniform lifts (generally not exceeding 8 inches in compacted thickness) by
mechanical means to at least 90 percent relative compaction (per ASTM Test Method D1557).
If trenches are shallow and the use of conventional equipment may result in damage to the
utilities; clean sand, having sand equivalent (SE) of 30 or greater, should be used to bed and
shade the utilities. Sand backfill should be densified. The densification may be
accomplished by jetting or flooding and then tamping to ensure adequate compaction. A
representative from LGC should observe, probe, and test the backfill to verify compliance
with the project specifications.
Within areas of shallow groundwater, trenching for the deeper utility improvements within the
roadway will likely encountered a shallow groundwater elevation. For planning purposes,
dewatering during trenching operations should be anticipated, especially where excavations
deeper than about 5 feet occur in close proximity to the anticipated shallow groundwater
Project No. 133023-05 Page 12 November 4, 2014
elevations. Regional groundwater should not adversely affect site development provided that
the recommendations presented in this report are properly incorporated into the design and
construction of the project. We recommend that periodic inspection be made by our engineer or
geologist during the grading operations and/or construction for the presence of groundwater. It
should be anticipated that the bottom of the trenches within these areas will also require
stabilization with a stabilization geotextile and rock, as necessary. Remedial measures, if any,
can be recommended on a case-by-case basis during the grading and construction operations.
4.2 Pavement Recommendations
4.2.1 ExistinR Pavement
Based on the previous site investigation/evaluation (by GeoSoils), the existing pavement
generally consists of a 6- to 8-inch thick layer of asphaltic concrete (AC) underlain by an
approximately 4-inch thick layer of what appears to be a recycled asphalt pavement (RAP). The
AC/RAP section was then observed to be underlain by a 12- to 18-inch layer of silty sand
(select fill or sub base), overlying clayey subgrade soils. The previous report indicates that a
subgrade sample was collected at the exploration locations for R-value testing. R-value testing
along El Camino Real resulted in a range of R-values from 8 to 31, with the majority of the
results being in the 14 to 16 range.
Based on the conclusions of the previous site evaluations and review and based on our
understanding of the proposed street improvements, the existing pavement areas should be
rehabilitated by grinding the upper 1 inch of existing asphaltic concrete and placement of a
minimum of 2 to 3 inch thick Hot Mix Asphalt pavement overlay.
4.2.2 New Pavement Areas
The pavement design and construction should be performed per the City of Carlsbad
construction standards. Based on our understanding and the city standards, El Camino Real
should be designed for a Traffic Index of 9.0.
Based on the previous site testing (GeoSoils, 2011 a), R-value testing along El Camino Real
resulted in a range of R-values from 8 to 31, with the majority of the results being in the 14 to
16 range. A preliminary R-value of 14 was considered in the new pavement design.
The R-value should be determined during the concluding stages of street grading, and the
final pavement section should be designed accordingly. Final pavement sections should be
confirmed based upon the final R-values and the City of Carlsbad minimum requirements.
Project No. 133023-05 Page 13 November 4, 2014
Recommended Minimum Pavement Sections
Traffic Index 9
Asphalt Concrete (in.) 6
Aggregate Base (in.) 17
The aggregate base material should conform to the specifications for Crushed Aggregate Base
(Standard Specifications for Public Works Construction —SSPWC Section 200-2) or Caltrans Class 2
Aggregate Base. The subgrade should achieve a minimum relative compaction of 95 percent through
the upper 12 inches. The base material should be compacted to achieve a minimum relative
compaction of 95 percent. Base and subgrade materials should be moisture-conditioned to a
relatively uniform moisture content at or slightly over optimum. The above recommendations are
considered applicable if complete removals of the compressible materials or minimum removals with
placement of stabilization geotextile are performed in the pavement areas.
- 4.3 Retaining Walls
4.3.1 Lateral Earth Pressures and Retaining Wall DesiRn Considerations
The following lateral earth pressures presented in the following table may be used for the
design of any future site retaining walls. We recommend low expansive soils for retaining wall
backfill if no onsite soils fit the required minimum parameters (i.e. a sand equivalent [SE]
greater than 30). The recommended lateral pressures for approved soils (expansion index less
than 30 per U.B.C. 18-I-B, less than 15 percent passing #200 sieve, and P1 less than 15) for
level or sloping backfill are presented on the table below. The recommended lateral pressures
for clean sand or approved select soils for level or sloping backfill are presented on the
following table.
Lateral Earth Pressures for Retaining Walls
Conditions
Equivalent Fluid Weight (pci)
Level Backfill 2:1 Backfill
Sloping Upwards
Seismic Earth Pressure (pci) *
___________________
Approved Select
Material
Approved Select
Material ____________________ Level 211:1V
Active 35 55 20 46
At-Rest 50 75 - -
Passive 250 - - -
- * For walls with a 6-foot (or greater) backfill height, the above seismic earth pressure
Project No. 133023-05 Page 14 November 4, 2014
should be added to the static pressures given in the table above. The seismic earth
pressure should be considered as an inverted triangular distribution with the resultant
acting at 0.6H in relation to the base of the retaining wall footing (where H is the
retained height). The aforementioned incremental seismic load was determined in
general accordance with the standard of practice in the industry (using the Mononobe-
Okabe method for active and Woods method for at-rest) for determining earth
pressures as a result of seismic events.
Embedded structural walls should be designed for lateral earth pressures exerted on them. The
magnitude of these pressures depends on the amount of deformation that the wall can yield
under load. If the wall can yield enough to mobilize the full shear strength of the soil, it can be
designed for "active" pressure. If the wall cannot yield under the applied load, the shear
strength of the soil cannot be mobilized and the earth pressure will be higher. Such walls should
be designed for "at-rest" conditions. If a structure moves toward the soils, the resulting
resistance developed by the soil is the "passive" resistance.
For design purposes, the recommended equivalent fluid pressure for each case for walls
founded above the static groundwater and backfllled with low expansive onsite or import soils
is provided in the table above. The equivalent fluid pressure values assume free-draining
conditions. The backfill soils should be compacted to at least 90 percent relative compaction.
The walls should be constructed and backfllled as soon as possible after back-cut excavation.
Prolonged exposure of back-cut slopes may result in some localized slope instability. If
conditions other than those assumed above are anticipated, the equivalent fluid pressure values
should be provided on an individual-case basis by the geotechnical engineer.
Surcharge loading effects from any adjacent structures should be evaluated by the geotechnical
and structural engineers. Surcharge loading on retaining walls should be considered when any
loads are located within a 1:1 (horizontal to vertical) projection from the base of the retaining
wall and should be added to the applicable lateral earth pressures. Where applicable, a
minimum uniform lateral pressure of 100 psf should be added to the appropriate lateral earth
pressures to account for typical vehicle traffic loading.
All retaining wall structures should be provided with appropriate drainage and appropriately
waterproofed. The outlet pipe should be sloped to drain to a suitable outlet. Typical wall
drainage design is illustrated on the attached Figure 1. It should be noted that the recommended
subdrain does not provide protection against seepage through the face of the wall and/or
efflorescence. Efflorescence is generally a white crystalline powder (discoloration) that results
when water, which contains soluble salts, migrates over a period of time through the face of a
retaining wall and evaporates. If such seepage or efflorescence is undesirable, retaining walls
should be waterproofed to reduce this potential.
For sliding resistance, the friction coefficient of 0.35 may be used at the concrete and soil
interface. Wall footings should be designed in accordance with structural considerations. The
passive resistance value may be increased by one-third when considering loads of short
duration such as wind or seismic loads. For short term loading (i.e. seismic) the allowable
bearing capacity may be increased by one-third for seismic loading.
Foundations for retaining walls in properly compacted fill should be embedded at least 18
inches below lowest adjacent grade. At this depth and a minimum of 12 inches in width, an
Project No. 133023-05 Page 15 November 4, 2014
allowable bearing capacity of 1,500 psf may be assumed. A factor of safety greater than 3 was
used in evaluating the above bearing capacity value. This value maybe increased by 250 psf
for each additional foot in depth and 100 psf for each additional foot of width to a maximum
value of 2,500 psf. All excavations should be made in accordance with Cal OSHA. Excavation
safety is the sole responsibility of the contractor.
- 4.3.2 Freestanding (Top-of-SloDe) Walls
Freestanding wall footings should be founded a minimum of 18 inches below the lowest
-. adjacent grade. To reduce the potential for unsightly cracks, we recommend inclusion of
construction joints at 10- to 20-foot intervals. Due to the potential creep of soils, where free
standing walls are constructed close to top-of-slope, some tilt of the wall should be
anticipated. To reduce the amount of tilt, a combination of grade beam and caisson
foundations may be used to support the wall. The system should consist of minimum 12-inch
diameter caissons placed at 8 feet maximum on centers, and each 8 feet long and connected
together at top with 12-inch by 12-inch grade beam. The geotechnical design parameters for
the caisson are shown on the attached Figure 2.
4.4 Corrosivitv to Concrete and Metal
The National Association of Corrosion Engineers (NACE) defines corrosion as "a deterioration of a
substance or its properties because of a reaction with its environment." From a geotechnical
viewpoint, the "environment" is the prevailing foundation soils and the "substances" are the
reinforced concrete foundations or various buried metallic elements such as rebar, piles, pipes, etc.,
which are in direct contact with or within close vicinity of the foundation soil.
In general, soil environments that are detrimental to concrete have high concentrations of soluble
sulfates and/or pH values of less than 5.5. ACI 318R-08 Table 4.3.1 provides specific guidelines for
the concrete mix design when the soluble sulfate content of the soils exceeds 0.1 percent by weight
or 1,000 ppm. The minimum amount of chloride ions in the soil environment that are corrosive to
steel, either in the form of reinforcement protected by concrete cover, or plain steel substructures
such as steel pipes or piles, is 500 ppm per California Test 532.
Based on previous site soil testing by others, the onsite soils are classified as having a negligible
sulfate exposure condition in accordance with AC! 318R-08 Table 4.3.1. As a preliminary
recommendation due to results of sulfate content testing, concrete in contact with onsite soils should
be designed in accordance with AC! 318R-08 Table 4.3.1 for the negligible category. It is also our
opinion that onsite soils should be considered severely corrosive to buried metals. Site grading will
redistribute the materials, which may result in soils with different corrosion potentials. Therefore,
the as-graded soil conditions should be verified with confirmatory sampling and testing during the
grading phase of the project.
Despite the minimum recommendation above, LGC is not a corrosion-engineering firm. Therefore,
we recommend that after site grading, consultation with a competent corrosion engineer be initiated
to evaluate the actual corrosion potential of the site and to provide recommendations to reduce the
corrosion potential with respect to the proposed improvements, as necessary. The recommendations
of the corrosion engineer may supersede the above requirements.
Project No. 133023-05 Page 16 November 4, 2014
4.5 Curb and Gutter and Sidewalk Recommendations
-- Concrete flatwork (such as curb and gutter and sidewalks) has a high potential for cracking due to
changes in soil volume related to soil-moisture fluctuations. To reduce the potential for excessive
cracking and lifting, concrete should be designed per the following recommendations. These
- guidelines will reduce the potential for irregular cracking and promote cracking along construction
joints, but will not eliminate all cracking or lifting. Thickening the concrete and/or adding
reinforcement will further reduce cosmetic distress.
Curb and Gutter should be designed per city standards, as necessary. The curb and gutter should be
anticipated to be underlain by the design aggregate base section used for the street section. Sidewalks
should be designed per city standards, as necessary. The sidewalk should be underlain by a minimum
of 4-inches of aggregate base.
The upper 6-inches of the subgrade for the curb and gutter and sidewalks should be compacted to a
minimum relative compaction of 95 percent, and the subgrade soil should be at or above the optimum
moisture content. Aggregate base material should be Crushed Aggregate Base or Crushed
Miscellaneous Base per SSPWC The "Greenbook" Section 200-2. Aggregate base material should be
compacted to a minimum relative compaction of 95 percent. Curb and gutter and sidewalks should be
provided with joints and expansion joins per usual practice/standards.
4.4 Control of Surface Water and Drainage Control
Positive drainage of surface water away from slopes, structures, and pavement areas is very important.
No water should be allowed to pond adjacent to the roadway. Overwatering of landscape and planter
areas must be avoided. Surface water runoff relative to project design is the purview of the project civil
engineer.
4.5 Plan Review, Construction Observation and TestinE
Geotechnical review of the future grading and improvement plans should be performed when final
plans becomes available from the project civil engineer.
The recommendations provided in this report are based on limited subsurface observations and
geotechnical analysis. The interpolated subsurface conditions should be checked in the field during
construction by a representative of LGC.
Construction observation and testing should also be performed by the geotechnical consultant during
future grading, excavations, preparation of pavement subgrade and placement of aggregate base, and
asphaltic concrete or when an unusual soil condition is encountered at the site. Final project drawings
should be reviewed by this office prior to construction.
Project No. 133023-05 Page 17 November 4, 2014
I
5.0 LIMITATIONS
Our services were performed using the degree of care and skill ordinarily exercised, under similar
circumstances, by reputable engineers and geologists practicing in this or similar localities. No other
warranty, expressed or implied, is made as to the conclusions and professional advice included in this report.
The samples taken and submitted for laboratory testing, the observations made and the in-situ field testing
performed are believed representative of the entire project; however, soil and geologic conditions revealed
by excavation may be different than our preliminary findings. If this occurs, the changed conditions must be
evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s)
recommended.
This report is issued with the understanding that it is the responsibility of the owner, or of his/her
representative, to ensure that the information and recommendations contained herein are brought to the
attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are
taken to see that the contractor and/or subcontractor properly implements the recommendations in the field.
The contractor and/or subcontractor should notify the owner if they consider any of the recommendations
presented herein to be unsafe.
The findings of this report are valid as of the present date. However, changes in the conditions of a property
can and do 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.
Project No. 133023-05 Page 18 November 4, 2014
APFENDJXA
References
California Division of Mines and Geology, 1986, Recommended guidelines for preparing engineering
geologic reports: California Division of Mines and Geology, Note 44
California Department of Transportation (Caltrans), 2012, Corrosion Guidelines, Version 2.0: Caltrans,
November 2012
Eisenberg, L.I., 1985, Pleistocene Faults and Marine Terraces, Northern San Diego County in Abbott, P.L.,
Editor, On the Manner of Deposition of the Eocene Strata in Northern San Diego County, San Diego
Association of Geologists, Field Trip Guidebook, pp. 86-91.
Eisenberg, L.I. and Abbott, P.L., 1985, Eocene Lithofacies and Geologic History, Northern San Diego
County in Abbott, P.L., ed., On the Manner of Deposition of the Eocene Strata in Northern San Diego
County: San Diego Association of Geologists, Field Trip Guidebook, pp. 19-35.
GeoSoils, Inc., 2011a, Geotechnical investigation for the planned improvement of El Camino Real, between
Cannon Road and Tamarack Avenue, Rancho Costera (Formerly Robertson Ranch West Village), Carlsbad,
San Diego County, California, W.O. 6145-E-SC, dated May Ii.
GeoSoils, Inc., 2011b, Geotechnical Review of coastal development permit plans for El Camino Real,
Rancho Costera Project, Carlsbad, San Diego County, California, W.O. 6145-A4, dated September 12.
GeoSoils, Inc., 2012a, Response to 2nd review for CDP 11-I0IHDP 11-02/SUP 11-03IHMP 11-04- ECR
southbound widening view comments (engineering), Rancho Costera project (Robertson Ranch West
Village), Carlsbad, San Diego County, California, W.O. 6145-A7/El-SC, dated January 3.
GeoSoils, Inc., 2012b, Rancho Costera and El Camino Real: bioswales/bioretention areas and desiltation
basins, dated January 13.
GeoSoils, Inc., 2012c, Draft Supplemental Analysis and Review of Slope Stability, Improvement of El
Camino Real, Rancho Costera Project (Robertson Ranch West Village), Carlsbad, San Diego County,
California, W.O. 6145-A7-SC, dated January 20.
http://www.earth.google.com,
http://www.historicaerials.com/
International Code Council, 2009, International Building Codes: International Code Council
Kennedy, M.P., and Tan, S.S., 2005, Geologic map of the Oceanside 30' by 60' quadrangle, California:
California Geological Survey, Regional Geologic Map No. 2, scale 1:100,000
Leighton and Associates, Inc., 1992, City of Carlsbad, Geotechnical Hazards Analysis and Mapping Study,
84 Sheets, dated November, 1992.
Project No. 133023-05 Page A-i November 4, 2014
LGC Valley, Inc., 2014, Geotechnical and Environmental Recommendations for Robertson Ranch West,
Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated April 29, 2014
LGC Valley, Inc., Undated, Unpublished In-House Geotechnical Data.
O'Day Consultants, 2014a, Grading and Improvement Plans for El Camino Real Widening, Robertson Ranch
West Village, CDP 11-10, Drawing No. 477-6,96 Sheets, dated March 3.
O'Day Consultants, 2014b, Tentative Map, Robertson Ranch West Village, Carlsbad Tract No. 13-03-2, 32
Sheets, dated March 5.
Tan, S.S., and Kennedy, M.P., 1996, Geologic Maps of the Northwestern Part of San Diego County,
California: California Division of Mines and Geology, DMG Open-File Report 96-02,2 Plates.
Tan, S.S., and Giffen, D.G., 1995, Landslide Hazards in the Northern Port of the San Diego Metropolitan
Area, San Diego County, California, Landslide Hazard Identification Map No. 35, Division of Mines and
Geology, Open-File Report No. 95-04.
United States Department of Agriculture, 1953, Aerial Photographs, Flight AXN-8M, Numbers 68, 69, 70, 9
101, 102, and 103, Scale approximately 1:20,000, dated April 11, 1953.
Weber, F.H., 1982, Recent Slope Failures, Ancient Landslides and Related Geology of the Northern-Central
Coastal Area, San Diego County, California: California Division of Mines and Geology, Open File Report
82-12LA, 77 p.
Wilson, K.L., 1972, Eocene and Related Geology of a Portion of the San Luis Rey and Encinitas
Quadrangles, San Diego County, California: Master Thesis, University of California at Riverside, 123 p.
Aerial Photographs Review
Date Source Flight Photo No(s)
1928 SD County 30 E3 to E6 and F2 to F5
1953 USDA AXN-8M 19 to 21
1975 SD County 34 12 to 14
1975 SD County 35 9 and 10
Project No. 133023-05 Page A-2 November 4, 2014
APPENDIX B
LGC VALLEY, INC
GENERAL EARTHWORKAND GRADING SPECIFICATIONS FOR ROUGH GRADING
1.0 General
1.1 Intent: These General Earthwork and Grading Specifications are for the grading and earthwork
shown on the approved grading plan(s) and/or indicated in the geotechnical report(s). These
Specifications are a part àf the recommendations contained in the geotechnical report(s). In
case of conflict, the specific recommendations in the geotechnical report shall supersede these
more general Specifications. Observations of the earthwork by the project Geotechnical
Consultant during the course of grading may result in new or revised recommendations that
could supersede these specifications or the recommendations in the geotechnical report(s).
1.2 The Geotechnical Consultant of Record: Prior to commencement of work, the owner shall
employ a qualified Geotechnical Consultant of Record (Geotechnical Consultant). The
Geotechnical Consultant shall be responsible for reviewing the approved geotechnical report(s)
and accepting the adequacy of the preliminary geotechnical findings, conclusions, and
recommendations prior to the commencement of the grading.
Prior to commencement of grading, the Geotechnical Consultant shall review the "work plan"
prepared by the Earthwork Contractor (Contractor) and schedule sufficient personnel to
perform the appropriate level of observation, mapping, and compaction testing.
During the grading and earthwork operations, the Geotechnical Consultant shall observe, map,
and document the subsurface exposures to verify the geotechnical design assumptions. If the
observed conditions are found to be significantly different than the interpreted assumptions
during the design phase, the Geotechnical Consultant shall inform the owner, recommend
appropriate changes in design to accommodate the observed conditions, and notify the review
agency where required.
The Geotechnical Consultant shall observe the moisture-conditioning and processing of the
subgrade and fill materials and perform relative compaction testing of fill to confirm that the
attained level of compaction is being accomplished as specified. The Geotechnical Consultant
shall provide the test results to the owner and the Contractor on a routine and frequent basis.
LGC Valley, Inc.
Genera! Earthwork and Grading Specifications
Page lof6
1.3 The Earthwork Contractor: The Earthwork Contractor (Contractor) shall be qualified,
experienced, and knowledgeable in earthwork logistics, preparation and processing of ground
to receive fill, moisture-conditioning and processing of fill, and compacting fill. The
Contractor shall review and accept the plans, geotechnical report(s), and these Specifications
prior to commencement of grading. The Contractor shall be solely responsible for performing
the grading in accordance with the project plans and specifications. The Contractor shall
prepare and submit to the owner and the Geotechnical Consultant a work plan that indicates the
sequence of earthwork grading, the number of "equipment" of work and the estimated
quantities of daily earthwork contemplated for the site prior to commencement of grading. The
Contractor shall inform the owner and the Geotechnical Consultant of changes in work
schedules and updates to the work plan at least 24 hours in advance of such changes so that
appropriate personnel will be available for observation and testing.. The Contractor shall not
assume that the Geotechnical Consultant is aware of all grading operations.
The Contractor shall have the sole responsibility to provide adequate equipment and methods to
accomplish the earthwork in accordance with the applicable grading codes and agency
ordinances, these Specifications, and the recommendations in the approved geotechnical
report(s) and grading plan(s). If, in the opinion of the Geotechnical Consultant, unsatisfactory
conditions, such as unsuitable soil, improper moisture condition, inadequate compaction,
insufficient buttress key size, adverse weather, etc., are resulting in a quality of work less than
required in these specifications, the Geotechnical Consultant shall reject the work and may
recommend to the owner that construction be stopped until the conditions are rectified. It is the
contractor's sole responsibility to provide proper fill compaction.
2.0 Preparation ofAreas to be Filled
2.1 ClearinE and GrubbinR: Vegetation, such as brush, grass, roots, and other deleterious material
shall be sufficiently removed and properly disposed of in a method acceptable to the owner,
governing agencies, and the Geotechnical Consultant.
The Geotechnical Consultant shall evaluate the extent of these removals depending on specific
site conditions. Earth fill material shall not contain more than 1 percent of organic materials
(by volume). No fill lift shall contain more than 10 percent of organic matter. Nesting of the
organic materials shall not be allowed.
If potentially hazardous materials are encountered, the Contractor shall stop work in the
affected area, and a hazardous material specialist shall be informed immediately for proper
evaluation and handling of these materials prior to continuing to work in that area.
LGC Valley, Inc.
General Earthwork and Grading Specifications
Page 2 of 6
As presently defined by the State of California, most refined petroleum products (gasoline,
diesel fuel, motor oil, grease, coolant, etc.) have chemical constituents that are considered to be
hazardous waste. As such, the indiscriminate dumping or spillage of these fluids onto the
ground may constitute a misdemeanor, punishable by fines and/or imprisonment, and shall not
be allowed. The contractor is responsible for all hazardous waste relating to his work. The
Geotechnical Consultant does not have expertise in this area. If hazardous waste is a concern,
then the Client should acquire the services of a qualified environmental assessor.
2.2 Processinz: Existing ground that has been declared satisfactory for support of fill by the
Geotechnical Consultant shall be scarified to a minimum depth of 6 inches. Existing ground
that is not satisfactory shall be overexcavated as specified in the following section.
Scarification shall continue until soils are broken down and free from oversize material and the
working surface is reasonably uniform, flat, and free from uneven features that would inhibit
uniform compaction.
2.3 Overe.rcavation: In addition to removals and overexcavations recommended in the approved
geotechnical report(s) and the grading plan, soft, loose, dry, saturated, spongy, organic-rich,
highly fractured or otherwise unsuitable ground shall be overexcavated to competent ground as
evaluated by the Geotechnical Consultant during grading.
2.4 Bench inR: Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to
vertical units), the ground shall be stepped or benched. Please see the Standard Details for a
graphic illustration. The lowest bench or key shall be a minimum of 15 feet wide and at least
2 feet deep, into competent material as evaluated by the Geotechnical Consultant. Other
benches shall be excavated a minimum height of 4 feet into competent material or as otherwise
recommended by the Geotechnical Consultant. Fill placed on ground sloping flatter than 5:1
shall also be benched or otherwise overexcavated to provide a flat subgrade for the fill.
2.5 Evaluation/Acceptance of Fill Areas: All areas to receive fill, including removal and
processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded,
and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill.
The Contractor shall obtain a written acceptance from the Geotechnical Consultant prior to fill
placement. A licensed surveyor shall provide the survey control for determining elevations of
processed areas, keys, and benches.
3.0 Fill Material
3.1 General: Material to be used as fill shall be essentially free from organic matter and other
deleterious substances evaluated and accepted by the Geotechnical Consultant prior to
placement. Soils of poor quality, such as those with unacceptable gradation, high expansion
potential, or low strength shall be placed in areas acceptable to the Geotechnical Consultant or
mixed with other soils to achieve satisfactory fill material.
LGC Valley, Inc.
General Earthwork and Grading Specifications
Page 3 of 6
3.2 Oversize: Oversize material defined as rock, or other irreducible material with a maximum
dimension greater than 8 inches, shall not be buried or placed in fill unless location, materials,
and placement methods are specifically accepted by the Geotechnical Consultant. Placement
operations shall be such that nesting of oversized material does not occur and such that oversize
material is completely surrounded by compacted or densified fill. Oversize material shall not
be placed within 10 vertical feet of finish grade or within 2 feet of future utilities or
underground construction.
3.3 Import: 'If importing of fill material is required for grading, proposed import material shall
meet the requirements of Section 3.1. The potential import source shall be given to the
Geotechnical Consultant at least 48 hours (2 working days) before importing begins so that its
suitability can be determined and appropriate tests performed.
4.0 Fill Placement and Compaction
4.1 Fill Layers: Approved fill material shall be placed in areas prepared to receive fill (per
Section 3.0) in near-horizontal layers not exceeding 8 inches in loose thickness. The
Geotechnical Consultant may accept thicker layers if testing indicates the grading procedures
can adequately compact the thicker layers. Each layer shall be spread evenly and mixed
thoroughly to attain relative uniformity of material and moisture throughout.
4.2 Fill Moisture ConditioninR: Fill soils shall be watered, dried back, blended, and/or mixed, as
necessary to attain a relatively uniform moisture content at or slightly over optimum.
Maximum density and optimum soil moisture content tests shall be performed in accordance
with the American Society of Testing and Materials (ASTM Test Method D1557-91).
4.3 Compaction OEM After each layer has been moisture-conditioned, mixed, and evenly spread,
it shall be uniformly compacted to not less than 90 percent of maximum dry density (ASTM
Test Method D1557-91). Compaction equipment shall be adequately sized and be either
specifically designed for soil compaction or of proven reliability to efficiently achieve the
specified level of compaction with uniformity.
4,4 Compaction of Fill Slopes: In addition to normal compaction procedures specified above,
compaction of slopes shall be accomplished by backrolling of slopes with sheeps-foot rollers at
increments of 3 to 4 feet in fill elevation, or by other methods producing satisfactory results
acceptable to the Geotechnical Consultant. Upon completion of grading, relative compaction
of the fill, out to the slope face, shall be at least 90 percent of maximum density per ASTM Test
Method D1557-91.
4.5 Compaction TeslinR: Field tests for moisture content and relative compaction of the fill soils
shall be performed by the Geotechnical Consultant. Location and frequency of tests shall be at
the Consultant's discretion based on field conditions encountered. Compaction test locations
LGC Valley, Inc.
General Earthwork and Grading Specifications
Page 4 of 6
will not necessarily be selected on a random basis. Test locations shall be selected to verify
adequacy of compaction levels in areas that are judged to be prone to inadequate compaction
(such as close to slope faces and at the fill/bedrock benches).
4.6 Frequency of Comvaction Testinz: Tests shall be taken at intervals not exceeding 2 feet in
vertical rise and/or 1,000 cubic yards of compacted fill soils embankment. In addition, as a
guideline, at least one test shall be taken on slope faces for each 5,000 square feet of slope face
and/or each 10 feet of vertical height of slope. The Contractor shall assure that fill construction
is such that the testing schedule can be accomplished by the Geotechnical Consultant. The
Contractor shall stop or slow down the earthwork construction if these minimum standards are
not met.
4.7 Compaction Test Locations: The Geotechnical Consultant shall document the approximate
elevation and horizontal coordinates of each test location. The Contractor shall coordinate with
the project surveyor to assure that sufficient grade stakes are established so that the
Geotechnical Consultant can determine the test locations with sufficient accuracy. At a
minimum, two grade stakes within a horizontal distance of 100 feet and vertically less than 5
feet apart from potential test locations shall be provided.
5.0 Subdrain Installation
Subdrain systems shall be installed in accordance with the approved geotechnical report(s), the grading
plan, and the Standard Details. The Geotechnical Consultant may recommend additional subdrains
and/or changes in subdrain extent, location, grade, or material depending on conditions encountered
during grading. All subdrains shall be surveyed by a land surveyor/civil engineer for line and grade
after installation and prior to burial. Sufficient time should be allowed by the Contractor for these
surveys.
6.0 Excavation
Excavations, as well as over-excavation for remedial purposes, shall be evaluated by the Geotechnical
Consultant during grading. Remedial removal depths shown on geotechnical plans are estimates only.
The actual extent of removal shall be determined by the Geotechnical Consultant based on the field
evaluation of exposed conditions during grading. Where fill-over-cut slopes are to be graded, the cut
portion of the slope shall be made, evaluated, and accepted by the Geotechnical Consultant prior to
placement of materials for construction of the fill portion of the slope, unless otherwise recommended
by the Geotechnical Consultant.
LGC Valley, Inc.
Genera! Earthwork and Grading Specifications
Page 5 of 6
7.0 Trench Backflils
7.1 The Contractor shall follow all OHSA and Cal/OSHA requirements for safety of trench
excavations.
7.2 All bedding and backfill of utility trenches shall be done in accordance with the applicable
provisions of Standard Specifications of Public Works Construction. Bedding material shall
have a Sand Equivalent greater than 30 (SE>30). The bedding shall be placed to 1 foot over
the top of the conduit and densifled by jetting. Backfill shall be placed and densifled to a
minimum of 90 percent of maximum from 1 foot above the top of the conduit to the surface.
7.3 The jetting of the bedding around the conduits shall be observed by the Geotechnical
Consultant.
7.4 The Geotechnical Consultant shall test the trench backfill for relative compaction. At least one
test should be made for every 300 feet of trench and 2 feet of fill.
7.5 Lift thickness of trench backfill shall not exceed those allowed in the Standard Specifications of
Public Works Construction unless the Contractor can demonstrate to the Geotechnical
Consultant that the fill lift can be compacted to the minimum relative compaction by his
alternative equipment and method.
LGC Valley, Inc.
General Earthwork and Grading Specifications
Page 6 of 6
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Drawn By : B!H
Job No. 133023-03 Geologist : RW
Engineer : BlH
Name :Toll/Robertson
PLATE I Date :11/4/14
Scale :1" = 100'
NOTES LGC VALLEY, INC.
Geotechnical Consulting
28532 Constellation Road 2420 Grand Avenue, Suite F2
Valencia, CA 91355 Vista, CA 92081
DATE
ON PLAN
GEOTECHNICAL MAP
TOLL BROTHERS: EL CAMIO REAL, ROBERTSO N
CARLSBAD, CALIFORNIA