HomeMy WebLinkAboutHDP 2020-0001; COLLEGE BOULEVARD MITIGATION; GEOLOGIC RECONNAISSANCE REPORT; 2014-10-13GEOLOGIC RECONNAISSANCE REPORT,
PROPOSED COLLEGE BOULEVARD
HABITAT MITIGATION SITE, CANTARINI RANCH,
CARLSBAD, CALIFORNIA
Prepared for:
BENT-WEST
5796 Armada Drive
Carlsbad, CA 92008
Project No. 10837.001
October 13, 2014
cf RECEIVED
FEB 1 ! 2020
CITY Or CARLSBAD
PLANNING DIVISION
----Leighton and Associates, Inc. ___ ..
A LEIGHTON GROUP COMPANY
Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
October 13, 2014
Bent-West
5796 Armada Drive
Carlsbad, CA 92008
Attention: Mr. Steve Powell
Project No. 10837.001
Subject: Geologic Reconnaissance Report
Proposed College Boulevard Habitat Mitigation Site
Cantarlnl Ranch, Carlsbad, California
In accordance with your request and authorization, we have conducted a geologic
reconnaissance study for the subject site in Carlsbad, California. Based on the results of
our geologic hazards reconnaissance evaluation, it is our opinion that the subject site
does not have significant geological constraints. The accompanying report presents a
summary of our study and provides our findings and conclusions regarding the subject
site.
If you have any questions regarding our report, please do not hesitate to cont me
directly at (858) 300-8491. We appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
William D. Olson, RCE 45289
Associate Engineer
Distribution: (2) Addressee
e . e , G 1349
President/Principal Geologist
3934 Murphy Canyon Road, Suite B205 • San Diego, CA 92123-4425
858.292.8030 • Fax 858.292.0771 • www.leightongroup.com
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TABLE OF CONTENTS
Section
1.0 INTRODUCTION .................................................................................................... 1
1.1 PURPOSE AND SCOPE OF SERVICES ........................................................................ 1
2.0 SITE CONDITIONS ................................................................................................ 2
2.1 SITE RECONNAISSANCE .......................................................................................... 2
2.1. 1 Site and Project Description .......................................................................... 2
2.1.2 Background Review ...................................................................................... 3
2.2 GEOLOGIC AND TECTONIC SETTING ......................................................................... 3
2.3 LOCAL GEOLOGIC SETTING ..................................................................................... 4
2.3.1 Undocumented Fill ....................................................................................... 4
2.3.2 Topsoil ........................................................................................................... 4
2.3.3 Alluvium ......................................................................................................... 4
2.3.4 Terrace Deposits .......................................................................................... 5
2.3.5 Santiago Formation ....................................................................................... 5
2.3.6 Geologic Structure ......................................................................................... 5
2.4 SURFACE WATER AND GROUND WATER .................................................................. 6
2.5 HYDROGEOLOGY AND SCOUR ................................................................................. 6
3.0 POTENTIAL GEOLOGIC HAZARDS .................................................................... 7
3.1 FAULTING AND SEISMICITY ...................................................................................... 7
3.1.1 Seismic Design Parameters .......................................................................... 7
3.1.2 Surface Rupture ............................................................................................ 8
3.1.3 Strong Ground Motion ................................................................................... 9
3.1.4 Liquefaction and Seismic Settlement ............................................................ 9
3.1.5 Lateral Spreading .......................................................................................... 9
3.2 LANDSLIDES ........................................................................................................ 10
3.3 FLOOD HAZARD ................................................................................................... 11
3.4 EXPANSIVE SOILS ................................................................................................ 11
3.5 CORROSIVE SOILS ............................................................................................... 11
4.0 CONCLUSIONS ................................................................................................... 12
5.0 PRELIMINARY RECOMMENDATIONS .............................................................. 13
5.1 EARTHWORK ....................................................................................................... 13
5.1.1 Site Preparation ........................................................................................... 13
5.1.2 Removal and Recompaction of Potentially Compressible Soils .................. 13
5.1.3 Structural Fills .............................................................................................. 14
5.1.4 Non-Structural Fills ...................................................................................... 14
6.0 LIMITATIONS ...................................................................................................... 15
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TABLE OF CONTENTS
TABLE
TABLE 1 -2013 CBC MAPPED SPECTRAL AccELERA TION PARAMETERS -PAGE 8
FIGURE
FIGURE 1 -SITE LOCATION MAP, REAR OF TEXT
PLATE 1 -PROPOSED COLLEGE BOULEVARD HABITAT MITIGATION SITE PLAN -IN POCKET
APPENDICES
APPENDIX A -REFERENCES
APPENDIX B -GENERAL EARTHWORK AND GRADING SPECIFICATIONS FOR ROUGH GRADING
APPENDIX C -ASFE SHEET
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1.0 INTRODUCTION
In accordance with your request and authorization, Leighton and Associates, Inc.
(Leighton) has performed a geologic reconnaissance study for the subject site located in
Carlsbad, California (Figure 1 ). We understand that the property is being considered for
future Habitat Mitigation Site.
The recommendations contained in this report are subject to the limitations presented in
Section 6.0. An information sheet prepared by ASFE (the Association of Engineering
Firms Practicing in the Geosciences) is also included as Appendix C. We recommend
that all individuals using this report read the limitations along with the attached
document.
1.1 Purpose and Scope of Services
This geologic reconnaissance study was completed to evaluate if the property is
potentially in an area with known (or a potential for) geologic hazards based on
existing site features and review of readily available geologic documents.
Leighton's scope of work consisted of:
• Researching in-house and published geotechnical, geologic, and seismic
reports and maps of the area;
• A reconnaissance of the site by our engineering geologist to observe
surface features and site geologic conditions;
• Stereoscopic analysis of air photos for assisting in the geologic
interpretation and identification of faults and other potential hazard-related
features;
• Review of available existing geology reports;
• Evaluation of geologic conditions from our site visit and data review; and
• Preparation of this written report with a description of the regional and site
geology including a geologic map, conclusions, regarding geologic
hazards on the property and preliminary recommendations.
Note that a subsurface exploration and laboratory testing of soil materials were
not included in the scope of this limited evaluation.
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2.0 SITE CONDITIONS
2.1 Site Reconnaissance
Our California Certified Engineering Geologist (CEG) conducted a site
reconnaissance on October 8, 2014 to evaluate and document current site
conditions. The site is located in the City of Carlsbad (see Figure 1 ), and consists
of a rough rectangular shaped property with the Agua Hedionda Creek running
through it.
2.1.1 Site and Project Description
The site, roughly 3 acres, is located north of College Boulevard and Sunny
Creek Road intersection, and is defined as Parcel C (Hunsaker &
Associates, 2014). Currently, the site is occupied by Equestrian Center
with fenced training and riding areas, stables, corrals, a residential unit
and several small facilities support structures (see Plate 1 ). In addition,
there are small to very large trees throughout the site.
The topography of the northern portion of the site (i.e., north of the existing
creek bed) slopes southward with elevation ranging from a high of 95 feet
above mean sea level (msl) to 71 feet msl. The topography of the
southern portion of the site is relatively level with elevation ranging from a
high of 66 feet to 73 feet msl. It should be noted that the existing creek
bed elevation ranges from approximately 53 feet to 60 feet msl at the west
and east ends, respectively.
In general, the proposed mitigation area will consists of regarding or
widening out of the Agua Hedionda Creek bed area to approximately 100
to 150 feet, adding a low flow channel, and grading 100-foot wide buffer
zones to the north and south to create expanded wetlands creek areas for
upland habitat mitigation. No structures are proposed. The buffer zones
will include cut slopes with varying gradual inclinations, with the exception
of a proposed 30-foot high 2H to 1V cut slope within the north central
portion of the site.
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Site Coordinates
N33.14700°
W117.12830°
2.1.2 Background Review
Specifically, our review included the following reports for the site:
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• Leighton and Associates, 2008, Foundation Report, College
Boulevard, Agua Hedionda Creek, Carlsbad, CA, Project No. 980160-
007, dated October 15, 2008
• Leighton and Associates, 2001, Updated Geotechnical Evaluation for
Cantarini Ranch, Carlsbad, California, Project No. 980160-003, dated
July 9, 2001.
2.2 Geologic and Tectonic Setting
The project area is situated in the Peninsular Ranges Geomorphic Province. This
geomorphic province encompasses an area that extends approximately 900
miles from the Transverse Ranges and the Los Angeles Basin south to the
southern tip of Baja California, and varies in width from approximately 30 to 100
miles (Norris and Webb, 1990). The province is characterized by mountainous
terrain on the east composed mostly of Mesozoic igneous and metamorphic
rocks, and relatively low-lying coastal terraces to the west underlain by late
Cretaceous, Tertiary, and Quaternary age sedimentary rocks. Most of the coastal
region of the County of San Diego, including the site, occur within this coastal
region and are underlain by sedimentary rock.
The Peninsular Ranges are traversed by several major active faults. The
Whittier-Elsinore, San Jacinto, and the San Andreas faults are major active fault
systems located northeast of the site, and the Rose Canyon, Newport-Inglewood
(offshore), and Coronado Bank are active faults located west to northwest of the
site (Jennings, 1994). Major tectonic activity associated with these and other
faults within this regional tectonic framework is right-lateral strike-slip movement.
These faults, as well as other faults in the region, have the potential for
generating strong ground motions at the project site. Further discussion of
faulting relative to the site is provided in the Faulting and Seismicity section of
this report.
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2.3 Local Geologic Setting
Formational materials (including the Quaternary-aged Terrace Deposits,
and Tertiary-aged Santiago Formation,) and surficial units (consisting of
alluvium, topsoil, and undocumented fill soils) were encountered during our
previous investigations and were observed during the recent site
reconnaissance. Each of the geologic units present on the site is described
below (youngest to oldest)
2.3.1 Undocumented Fill
Undocumented fill soils were observed across the site and generally
associated with the original grading of the site and prior development.
All existing undocumented fills located on the site are considered
potentially compressible and unsuitable in their present state for
structural support. These soils should be removed if structural
improvements or structural fill are being proposed within the limits of
grading. The fills are anticipated to be less than 10 feet in thickness.
2.3.2 Topsoil
Topsoil also mantles portions of the site, and consists predominantly of
light brown to brown, damp to moist, stiff, sandy to silty clay and some
clayey to silty sands. These soils were generally porous and contained
scattered roots and organics. The potentially compressible topsoil is
estimated to be approximately 1 to 4 feet in thickness; however,
localized areas of thicker accumulations of topsoil may be encountered
during grading. The topsoil is not suitable for support of compacted fills
and a structural loads should be removed during grading.
2.3.3 Alluvium
Alluvium underlies a majority of the site and area south of the existing
Agua Hedionda Creek bed. The alluvial soils are usually thickest in the
center of drainages and often interfinger with colluvial soils on the
drainage margins forming wedges of alluvial and colluvial soils that thin
away from the drainages. These soils typically consist of brown, damp
to wet, loose to medium dense/stiff, silty sands, sandy clays and silty
clays. The alluvium typically is moderately porous and often contains
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localized zones of moderate to abundant roots and other organic
matter. The alluvium is considered potentially compressible and is
recommended to be removed to competent formational material, if
structural fills or settlement sensitivity improvements are being proposed.
Note the in our borings and soundings for the proposed College
Boulevard bridge (Leighton, 2007), the alluvium was encountered to a
depth of between 13 to 19 feet (or an approximate elevation of 54 to 61
feet msl) along the north bridge abutment location and to a depth of
between 58 to 72 feet (or an approximate elevation of 2 to 15 feet
msl) along the south bridge abutment location. The alluvium and
colluvium may be recompacted and used as structural fill provided
detrimental materials are removed.
2.3.4 Terrace Deposits
Pleistocene-aged Terrace Deposits exist on the lower hilltops
(located in the northern portion of the site) unconformably overlying the
Santiago Formation. These deposits are present in a limited extent
above an approximate elevation of 75 feet (msl) on the site. The soil
comprising the Terrace Deposits is generally composed of course sand to
a sandy cobble conglomerate. This material typically has a low potential
for expansion and may be recompacted for use as structural fill.
2.3.5 Santiago Formation
In general, the entire site and northern slope area is underlain at depth by
bedrock material consisting of the Santiago Formation that is composed of
interbedded brown, dense to very dense, silty, fine to coarse sandstone
and gray brown, moist, hard, sandy claystones.
2.3.6 Geologic Structure
Review of the geologic literature applicable to the site (Appendix A), our
professional experience on sites with similar soils, and geologic mapping
of the site, indicate the on-site geologic units are generally flat-lying and
massively bedded with occasional randomly oriented jointing. Based on
the limited subsurface data and our experience with the onsite units,
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bedding within the formational soils is anticipated to be slightly dipping (10
degrees or less) toward the west.
No faults have been mapped on the site nor were any encountered during
our field study. Minor to moderate jointing of the near surface soils may
also be present on the hillsides of the site. Jointing, if encountered, is
anticipated to be randomly oriented and moderate to steeply dipping.
2.4 Surface Water and Ground Water
Surface water was observed flowing within the existing Agua Hedionda Creek
bed during our site visit. Therefore, shallow groundwater (i.e., approximate
elevation of 60 feet msl) and seeps are anticipated to be encountered during
grading, and should be considered as potential construction issue in proposed
grading of the habitat mitigation area. Note that surface water and ground water
table is expected to fluctuate with seasonal variations in rainfall, irrigation
practices, and local perched ground water conditions may exist.
2.5 Hydrogeology and Scour
Based on our previous investigations and site reconnaissance, the near surface
soils within the site and proposed habitat mitigation area are potentially erodible
alluvial deposits and subject to scour when subjected to concentrated and high
velocity flows. Therefore, we recommend that a hydrogeology study and scour
analysis be performed by the project civil engineer, and, if needed, design of
scour countermeasures should be development.
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3.0 POTENTIAL GEOLOGIC HAZARDS
These hazards include, surface rupture, seismic shaking, landslides, liquefaction,
seismically induced settlement, flooding, and expansive and corrosive soils. The
following sections discuss these hazards and their potential at this site in more detail:
3.1 Faulting and Seismicity
Our discussion of faults on the site is prefaced with a discussion of California
legislation and policies concerning the classification and land-use criteria
associated with faults. By definition of the California Geological Survey, an active
fault is a fault which has had surface displacement within Holocene time (about
the last 11,000 years). The state geologist has defined a potentially active fault
as any fault considered to have been active during Quaternary time (last
1,600,000 years). This definition is used in delineating Earthquake Fault Zones
as mandated by the Alquist-Priolo Geologic Hazards Zones Act of 1972 and most
recently revised in 2007 (Bryant and Hart, 2007). The intent of this act is to
assure that unwise urban development and certain habitable structures do not
occur across the traces of active faults. The subject site is not included within any
Earthquake Fault Zones as created by the Alquist-Priolo Act.
Our review of available geologic literature (Appendix A) indicates that there are
no known major or active faults on or in the immediate vicinity of the site. The
nearest active regional fault is the offshore segment of the Rose Canyon Fault
Zone located approximately 7 miles west of the site.
3.1.1 Seismic Design Parameters
The site can be considered to lie within a seismically active region, as can
all of Southern California. The effect of seismic shaking may be mitigated
by adhering to the California Building Code and state-of-the-art seismic
design practices of the Structural Engineers Association of California.
Provided below in the Table 1 are the risk-targeted spectral acceleration
parameters for the project determined in accordance with the 2013
California Building Code (CBSC, 2013a) and the USGS Worldwide
Seismic Design Values tool (Version 3.1.0).
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Table 1
2013 CBC Mapped Spectral Acceleration Parameters
Site Class D
Site Coefficients Fa= 1.087
Fv= 1.598
Mapped MCER Spectral Ss = 1.032g
Accelerations S1 = 0.402g
Site Modified MCER Spectral SMs = 1.122g
Accelerations SM1 = 0.643g
Design Spectral Accelerations Sos= 0.748g
So1 = 0.424g
Utilizing ASCE Standard 7-10, in accordance with Section 11.8.3, the
following additional parameters for the peak horizontal ground
acceleration are associated with the Geometric Mean Maximum
Considered Earthquake (MCEG). The mapped MCEG peak ground
acceleration (PGA) is 0.387g for the site. For a Site Class D, the FPGA is
1.113 and the mapped peak ground acceleration adjusted for Site Class
effects (PGAM) is 0.43g for the site.
3.1.2 Surface Rupture
The Rose Canyon fault is the closest mapped active fault, and is located
approximately 6.9 miles west of the site (CGS, 2003). Therefore, the
potential for ground rupture due to faulting at the site is considered very
low.
Ground lurching is defined as movement of low density soil materials on a
bluff, steep slope, or embankment due to earthquake shaking. Since the
site doesn't contain oversteepened slopes or artificial fill slopes, the risk of
ground lurch is low.
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3.1.3 Strong Ground Motion
Like all of Southern California, severe ground shaking is most likely to
occur during an earthquake on one of the regional active faults in the area.
The effect of seismic shaking may be mitigated by adhering to the
California Building Code or state-of-the-art seismic design parameters of
the Structural Engineers Association of California.
3.1.4 Liquefaction and Seismic Settlement
Liquefaction of soils can be caused by strong vibratory motion due to
earthquakes. Both research and historical data indicate that loose,
saturated, granular soils are susceptible to liquefaction and dynamic
settlement. Liquefaction is typified by a reduction in of shear strength in
the affected soil layer. Liquefaction may be manifested by excessive
settlement, sand boils, and bearing failure.
A liquefaction analysis was performed for the proposed College
Boulevard Bridge (Leighton, 2008), which is located east of the site. In
summary, portions of the alluvial materials beneath the southern
abutment area, as encountered in our borings and CPT soundings, are
considered to contain liquefaction susceptible layers at the anticipated
ground motion. Considering the potential for liquefaction at the site,
additional subsurface investigation should be considered, if settlement
sensitivity improvements are being proposed.
The post-liquefaction settlements indicate that dynamic settlements range
from 3 to 9 inches in the area of the southern abutment, which could be
representative of the southern portion of the site. Dynamic settlements in
the area of the northern abutment are anticipated to be less than 1 /4 of an
inch, which could be representative of the north-central portion of the site.
3.1.5 Lateral Spreading
For the proposed College Boulevard Bridge (Leighton, 2008), an
evaluation of lateral spread due to liquefaction was performed and
include parameters such as earthquake magnitude, distance of the
earthquake from the site, slope height and angle, the thickness of
liquefiable soil, and gradation characteristics of the soil. In summary,
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the analysis indicated that there was a potential for lateral displacement
at the southern embankment (i.e., representative of the southern portion
of the site) and that mitigation (i.e., ground improvement or treatment)
should be considered. However, considering the proposed land use
as habitat mitigation with varying gradual cut and fill slopes, ground
improvement or treatment would not seem appropriate, unless
structural fills or settlement sensitivity improvements are being proposed.
3.2 Landslides
Landslides are deep-seated ground failures (several tens to hundreds of feet
deep) in which a large arcuate shaped section of a slope detaches and slides
downhill. Landslides are not to be confused with minor slope failures (slumps),
which are usually limited to the topsoil zone and can occur on slopes composed
of almost any geologic material. Landslides can cause damage to structures both
above and below the slide mass. Structures above the slide area are typically
damaged by undermining of foundations. Areas below a slide mass can be
damaged by being overridden and crushed by the failed slope material.
Several formations within the San Diego region are particularly prone to
landsliding. These formations generally have high clay content and mobilize
when they become saturated with water. Other factors, such as steeply dipping
bedding that project out of the face of the slope and/or the presence of fracture
planes, will also increase the potential for landsliding.
No active landslides or indications of deep-seated landsliding were noted at the
site during our field reconnaissance or our review of available geologic literature,
topographic maps, and stereoscopic aerial photographs. Furthermore, our field
reconnaissance and the local geologic maps indicate the site is underlain by
favorable oriented geologic structure. Therefore, the potential for significant
landslides or large-scale slope instability at the site is generally considered low.
However, local portions of the site are underlain by less favorable geologic
materials, and will therefore have an increased risk for slope stability depending
on the proposed project design.
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3.3 Flood Hazard
According to a Federal Emergency Management Agency (FEMA) flood insurance
rate map (FEMA, 2012), the site is located within the 100-year flood zone and is
defined as a Zone AE with a flood water surface elevation of 7 4 feet.
3.4 Expansive Soils
Expansive soils are characterized by their ability to undergo significant volume
changes (shrink or swell) due to variations in moisture content. Changes in soil
moisture content can result from precipitation, landscape irrigation, utility
leakage, roof drainage, perched groundwater, drought, or other factors and may
result in unacceptable settlement or heave of structures or concrete slabs
supported on grade.
Therefore, based on the results of our background review and site
reconnaissance, the majority of the onsite soils are expected to have a low to
moderate expansion potential. However, some of the on-site alluvial soils and
possibly the claystone of the Santiago Formation may be highly expansive.
3.5 Corrosive Soils
Corrosive soils are characterized by their ability to degrade concrete and corrode
ferrous materials in contact with water or soil. In particular, concrete is
susceptible to corrosion when it is in contact with soil or water that contains high
concentrations of soluble sulfates which can result in chemical deterioration of
the concrete. In addition, regarding ferrous metals, electrical resistivity of the soil
can affect the soils corrosive effects.
Previous laboratory tests carried out on selected soil samples collected from the
subject site indicate that the soils are of negligible to low soluble sulfate content,
neutral pH and moderate electrical resistivity. These findings indicate that the
corrosive effects of the onsite soils tested to steel and concrete components are
expected to be low to moderate.
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4.0 CONCLUSIONS
Based on the results of our geologic reconnaissance study of the site, it is our opinion
that the development of the proposed habitat mitigation area is feasible from a
geotechnical viewpoint, provided the following conclusions and preliminary
recommendations are incorporated into the project plans and specifications. Note that if
settlement sensitivity improvements are being proposed, addition site specific
subsurface investigation will be required.
The following is a summary of the significant geotechnical factors that we expect may
affect development of the proposed habitat mitigation area.
• All existing undocumented fills, topsoil and alluvium are considered
potentially compressible and unsuitable in their present state for structural
support. These soils should be removed if structural improvements or
structural fill are being proposed within the limits of grading.
• Shallow groundwater (i.e., approximate elevation of 60 feet msl) and seeps are
anticipated to be encountered during grading, and should be considered as
potential construction issue in proposed grading of the habitat mitigation area.
• The near surface soils within the proposed habitat mitigation area are potentially
erodible alluvial deposits and subject to scour when subjected to concentrated
and high velocity flows. Therefore, we recommend that a hydrogeology study and
scour analysis be performed by the project civil engineer, and, if needed, design
of scour countermeasures should be development
• There is a potential for liquefaction and lateral spread due to liquefaction at the
site within the saturate alluvium. Additional subsurface investigation should be
performed, if settlement sensitivity improvements are being proposed.
• The potential for significant landslides or large-scale slope instability at the site is
considered low. However, local portions of the site are underlain by less
favorable geologic materials may be present, and geological mapping should be
performed during site grading.
• The site is located within the 100-year flood zone and is defined as a Zone AE
with a flood water surface elevation of 74 feet.
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5.0 PRELIMINARY RECOMMENDATIONS
Based on the results of our geologic reconnaissance study, we are providing the
following preliminary recommendations to assist in the planning and preliminary design
of the proposed project. Please note that the following preliminary recommendations are
for planning purposes only.
5.1 Earthwork
We anticipate that earthwork at the site will consist of site preparation,
excavations, and export of excess material. In general, the placement of
structural fill soils is generally not proposed. We recommend that earthwork on
the site be performed in accordance with the following recommendations, in
accordance with "Greenbook" specifications, the County of San Diego grading
requirements, and the General Earthwork and Grading Specifications included in
Appendix C. In case of conflict, the following recommendations shall supersede
those in Appendix C. It should be noted that the guidelines provided in Appendix
Care for planning purposes only.
5.1.1 Site Preparation
Prior to grading, the proposed development of the site should be cleared
of surface and subsurface obstructions, including any existing debris and
undocumented or loose fill soils, and stripped of vegetation. Removed
vegetation and debris should be properly disposed off site. All areas to
receive structural fill and/or other surface improvements should be
scarified to a minimum depth of 6 inches, brought to near-optimum
moisture conditions, and recompacted to at least 90 percent relative
compaction (based on ASTM Test Method D1557-96).
5.1.2 Removal and Recompaction of Potentially Compressible Soils
The undocumented fill and alluvium soils that occur on site are potentially
compressible in their present state and may settle under the surcharge of
fills or foundation loadings. In areas that will receive additional fill soils that
will support settlement-sensitive structures or other improvements (such
as roadway utility, retaining walls, lines, etc.), these soils should be
removed down to competent material determined by the geotechnical
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consultant, moisture-conditioned, and recompacted to a minimum
90 percent relative compaction (based on ASTM D1557-96) prior to
placing fill. The removal limit should be established by a 1 : 1 projection
from the edge of fill soils supporting settlement-sensitive structures
downward and outward to competent material identified by the
geotechnical consultant. Fill soils should be free of debris and organic
materials (trees, shrubs, stumps, roots, leaves, and mulch derived from
vegetation).
5.1.3 Structural Fills
The onsite soils, excluding topsoil, are generally suitable for use as
compacted fill provided they are free of organic materials and debris.
Although not currectly proposed, areas 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 D1557-96). 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 not exceeding 8 inches in thickness. Fill soils should
be placed at a minimum of 90 percent relative compaction (based on
ASTM D1557-96) above optimum moisture content. Placement and
compaction of fill should be performed in accordance with local grading
ordinances under the observation and testing of the geotechnical
consultant.
5.1.4 Non-Structural Fills
For non-structural fill areas such as the habitat mitigation area and areas
with slopes with inclinations less than or equal to 3 to 1, no removal will be
required prior to placement of fill. The non-structural fill should be moisture
conditioned to near optimum moisture content and compacted to 85
percent or more relative compaction, in accordance with ASTM D 1557.
Although the optimum lift thickness for fill soils will be dependent on the
type of compaction equipment utilized, fill should generally be placed in
uniform lifts not exceeding approximately 12 inches in loose thickness.
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6.0 LIMITATIONS
The geologic analyses presented in this geologic reconnaissance report have been
conducted in general accordance with current practice and the standard of care
exercised by geologic consultants performing similar tasks in the project area. No other
warranty, expressed or implied, is made regarding the conclusions, recommendations,
and opinions presented in this report.
Please also note that our evaluation was limited to assessment of the geologic aspects
of the project, and did not include evaluation of structural issues, environmental
concerns or the presence of hazardous materials. Our conclusions, recommendations
and opinions are based on an analysis of the observed site conditions, and our review
of the referenced geologic literature and reports. If geologic conditions different from
those described in this report are encountered, our office should be notified and
additional recommendations, if warranted, will be provided upon request.
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FIGURE
0 2.000
Feet
Project: 10837.001 Eng/Geol: WOO/MRS
Scale: 1 • = 2,000 ' Date: October 2014
Base Map. ESRI ArcGIS Online 2014
Thematic Information: Leig,ton
Author. (mmurphy)
SITE LOCATION MAP
College Blvd . Habitat Mitigation Site
Cantarini Ranch
Carlsbad, California
MapSaYed H V'draftl'lg\10837\001\Mlpt\10837001_Fig1_SLM_2014-10.13 mxd on 1Clt1Y201◄ 8 52 10AM
Leighton
PLATE
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APPENDIX A
REFERENCES
APPENDIX A
REFERENCES
10837.001
Bryant, W. A. and Hart, E.W., 2007, Fault Rupture Hazard Zones in California, Alquist-
Priolo Special Studies Zones Act of 1972 with Index to Special Study Zone
Maps, Department of Conservation, Division of Mines and Geology, Special
Publication 42, dated 1997 with 2007 Interim Revision.
California Building and Safety Commission (CBSC), 2013, California Building Code.
California Geologic Survey (CGS), 2000, Digital Images of Official Maps of Alquist-
Priolo Earthquake Fault Zones of California, Southern Region, DMG CD 2000-02.
County of San Diego, 2007, Guidelines for Determining Significance, Geologic Hazards,
dated July 30, 2007.
Federal Emergency Management Agency (FEMA), 2012, Flood Insurance Rate Map
(FIRM), Carlsbad, California, San Diego County, Panel 768 of 2375 dated May
16.
Hart, E.W., and Bryant, W.A., 2007, Special Publication 42, Fault Rupture Hazard
Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to
Earthquake Fault Zone Maps, Interim Revision 2007.
Hunsaker & Associates, 2014, Preliminary Habitat Mitigation Site Plan, received
September 30, 2014.
Kennedy, M.P., and Tan, S.S., 2007, Geologic Map of the Oceanside 30'x60'
Quadrangle, California, California Geologic Survey, 1:100,000 scale.
Leighton and Associates, 2008, Foundation Report, College Boulevard, Agua Hedionda
Creek, Carlsbad, Ca, Project No. 980160-007, dated October 15, 2008
Leighton and Associates, 2001, Updated Geotechnical Evaluation for Cantarini Ranch,
Carlsbad, California, Project No. 980160-003, dated July 9, 2001.
A-1
0
APPENDIX B
GENERAL EARTHWORK AND GRADING SPECIFICATIONS
FOR ROUGH GRADING
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
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 of 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 the Geotechnical
Consultant of Record (Geotechnical Consultant). The Geotechnical
Consultants 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. Subsurface
areas to be geotechnically observed, mapped, elevations recorded, and/or
tested include natural ground after it has been cleared for receiving fill but
before fill is placed, bottoms of all "remedial removal" areas, all key
bottoms, and benches made on sloping ground to receive fill.
The Geotechnical Consultant shall observe the moisture-conditioning and
processing of the subgrade and fill materials and perform relative
compaction testing of fill to determine the attained level of compaction.
The Geotechnical Consultant shall provide the test results to the owner
and the Contractor on a routine and frequent basis.
-1-
0
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
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 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 "spreads" 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 observations and tests can be planned and accomplished.
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.
2.0 Preparation of Areas to be Filled
2.1 Clearing and Grubbing
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.
-2-
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
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 5 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.
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.
2.2 Processing
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 of large clay lumps or clods and the working
surface is reasonably uniform, flat, and free of uneven features that would
inhibit uniform compaction.
2.3 Overexcavation
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 Benching
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
-3-
C 0
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
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 of 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.
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-
-
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
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 Conditioning
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).
4.3 Compaction of Fill
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). 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 sheepsfoot
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.
4.5 Compaction Testing
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 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
-5-
0
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
inadequate compaction (such as close to slope faces and at the
fill/bedrock benches).
4.6 Frequency of Compaction Testing
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.
-6-
LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
7.0 Trench Backfills
7.1 Safety
The Contractor shall follow all OSHA and Cal/OSHA requirements for
safety of trench excavations.
7 .2 Bedding and Backfill
All bedding and backfill of utility trenches shall be performed 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 densified. Backfill shall be placed and
densified to a minimum of 90 percent of relative compaction from 1 foot
above the top of the conduit to the surface.
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.
7.3 Lift Thickness
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.
7.4 Observation and Testing
The densification of the bedding around the conduits shall be observed by
the Geotechnical Consultant.
-7-
FILL SLOPE
PROJECTED PLANE 1: 1
(HORIZONTAL: VERTICAL)
MAXIMUM FROM TOE
OF SLOPE TO
APPROVED GROUND
EXISTING
GROUND SURFACE
p4p;;.::.:a, ---
ALL-OVER-CUT SLOPE CTED:-:-:----.
BENCH HEIGHT
EXISTING
GROUND SURFJCE
-_. ----( 4 FEET TYPICAL) ---~n~ir·C::::
5 FEET MIN. I
LOWEST
BENCH (KEY)
T FACE
REMOVE
UNSUITABLE
MATERIAL
SHALL BE CONSTRUCTED PRIOR TO .,-
FILL PLACEMENT TO ALLOW VIEWING //
OF GEOLOGIC CONDITIONS
EXISTING-/
CUT-OVER-FLL SLOPE GROUND
SURF ACE£ _ _-_-
UT FACE SHALL BE
CONSTRUCTED PRIOR
TO FILL PLACEMENT
PROJECTED PLANE
1 TO 1 MAXIMUM
FRO~ TOE OF SLOPE
TO APPROVED GROUND
,t,.-·
OVERBUILD AND---~
TRIM BACK REMOVE
UNSUITABLE
MATERIAL
BENCH HEIGHT
( 4 FEET TYPICAL)
15 FEET MIN. BENCHING SHALL BE DONE WHEN SLOPE'S
2 FEET MIN. LOWEST ANGLE IS EQUAL TO OR GREATER THAN 5: 1.
KEY DEPTH BENCH (KEY) MINIMUM BENCH HEIGHT SHALL BE 4 FEET
AND MINIMUM FILL WIDTH SHALL BE 9 FEET.
KEYING AND BENCHING
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL A
FINISH GRADE
-... --------------------------------------------------·-------------------------------------------------------
OVERSIZE WINDROW
• OVERSIZE ROCK IS LARGER THAN
8 INCHES IN LARGEST DIMENSION.
• EXCAVATE A TRENCH IN THE COMPACTED
FILL DEEP ENOUGH TO BURY ALL THE
ROCK.
• BACKFILL WITH GRANULAR SOIL JETTED
OR FLOODED IN PLACE TO FILL ALL THE
VOIDS.
• DO NOT BURY ROCK WITHIN 10 FEET OF
FINISH GRADE.
• WINDROW OF BURIED ROCK SHALL BE
PARALLEL TO THE FINISHED SLOPE.
GRANULAR MA TERI AL TO BE
OENSIFIEO IN PLACE BY
FLOODING OR JETTING.
DETAIL
JETTED OR FLOODED -----
GRANULAR MATERI AL
TYPICAL PROFILE ALONG WINDROW
OVERSIZE ROCK
DISPOSAL
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL B
' '-. '---EXISTING
SUBDRAIN
TRENCH
SEE DETAIL BELOW
FILTER FABRIC
REMOVE
UNSUITABLE
MATERIAL
6" MIN.
OVERLAP
(MIRAFI 140N OR APPROVED
EQUIVALENT)•
CAL TRANS CLASS 2 PERMEABLE 1/,1/
OR /12 ROCK (9FT".J/FT) WR AP : • •.
IN FILTER FABRIC ·: .• .... . . . . .. ·. ~-
-:! :.:.... .:., IN. BEDDING
DESIGN FINISH
GRADE
SUBPBAIN PEJAIL
--------
t
COLLECTOR PIPE SHALL
BE MINIMUM 6" DIAMETER
SCHEDULE 40 PVC PERFORATED
PIPE. SEE STANDARD DETAIL D
FOR PIPE SPECIFICATIONS
------------------------1 O' MIN FILTER FABRIC
----------------• BACKFILL (MIRAFI 140N OR APPROVED .-.·-. ---••• ·-•••• ::: -·.·.-.·. EQUIVALENT)
-• -•• _-_·:·:~~~~ACTED tLL"-·-· .-.·.-.----:-_
:::::::::::::::::-:--•• ' ••. • .' • • • • : • • · . -CAL TRANS CLASS 2 PERMEABLE
---·------------• ; •: '•: ' ; .' :· • ' • :· •. : • •• OR /12 ROCK (9FT"J/FT) WRAPPED
I
I • i-----• ' IN FILTER FABRIC I-20' MIN. 5' MIN. I PERF"ORA TED .
· ' • 6" 0 MIN . PIPE NONPERFORATED 6"0 MIN.
DETAIL Of CANYoN SUBPBAIN OUD,EJ
CANYON SUBDRAINS GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL C
OUTLET PIPES
4" 0 NONPERFORATEO PIPE,
100' ~AX. O.C. HORIZONTALLY,
30' MAX O.C. V£RTICALL Y
-.. ---.... -::::=-%-1.41
---------·-------.-:=:: .·.·. === .·.·.·.-.--·-·-------·-·-·.-.----·-·-:~x-·
_-:-: =: =:-:-: =:=:=:: :=: =:=:=:= :=: =:=: =:::: := :=:=:::-:-/ _-:=:=:=:=:=:toMPACf(O-rici.;:-:-:-:-:-:-:-· . -
----====~=~~t~~~t~~~~~~tII~t~tttI= -.k :t;
. _.-: ::: :: :::: ·:::::: :: :::::: :-;2 % M_f ~ .-:::: :-:-:-:-:::::::-: -:--7
12" MIN. OVERLAP
FROM THE TOP HOG
RING TIED EVERY
6 FEET
CAL TRANS CLASS II
PERMEABLE OR #2
ROCK (3 FTA3/FT)
WRAPPED IN FILTER
FABRIC
PROVIDE POSITIVE
SEAL AT THE
JOINT
15' MIN.
TRENCH
LOWEST SUBORAIN SHOULD
BE SITUATED AS LOW AS
POSSIBLE TO ALLOW
SUITABLE OUTLET
T-CONNECTION
FOR COLLECTOR
PIPE TO OUTLET PIPE
4• .0
PERFORATED
PIPE
~--4" MIN.
FIL TE-R FABRIC
ENVELOPE (MIRAFI
I 40 OR APPROVED
EQUIVALENT)
BEDDING
SUBDRAIN TRENCH DETAIL
SUBDRAIN INSTALLATION -subdroin collector pipe shall be installed with perforation down or,
unless otherwise designated by the geotechnic:ol consultant Outlet pipes shall be non-perforated
pipe. The subdroin pipe sholl hove ot leost 8 perforations uniformly spoced per foot. Perforation
shall be 1 /4" to 1 /2" if drill holes ore used. All subdroin pipes sholl hove o gradient of ot
leost 27. towords the outlet.
SUBO~AIN PIPE -Subdroin pipe shall be ASTt.4 D2751, SOR 23,5 or ASTt.4 01527, Schedule 40, or
ASTM 03034, SOR 23.5, Schedule 40 Folyvinyt Chloride Plostic (PVC) pipe.
All outlet pipe shall be placed in o trench no wider thon twice the subdroin pipe.
BUTTRESS OR
REPLACEMENT
FILL SUBDRAINS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL D
CUT-FILL TRANSITION LOT OVEREXCAVA TION
TRANSITION LOT FILLS
REMOVE
UNSUITABLE
GROUND \_ ------
-------5'
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL E
--------
RETAINING WALL
WALL WATERPROOFING ~
PER ARCHITECT'S
SPECIFICATIONS
FINISH GRADE
······------------------------------·=-:-:-:-:-:-:-:-:-:-:-:-:-cOMP AC TEO FILL·-:-:-:-:-:-:-:
-------------
SOIL BACKFILL, COMPACTED TO
90 PERCENT RELATIVE COMPACTION
BASED ON ASTM D1557
COMPETENT BEDROCK OR MATERIAL
AS EVALUATED BY THE GEOTECHNICAL
CONSULTANT
NOTE: UPON REVIEW BY THE GEOTECHNICAL CONSUL TANT,
COMPOSITE DRAINAGE PRODUCTS SUCH AS MIRADRAIN OR
J-DRAIN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR
CLASS 2 PERMEABLE MATERIAL. INSTALLATION SHOULD BE
PERFORMED IN ACCORDANCE WITH MANUFACTURER'S
SPECIFICATIONS.
RETAINING WALL
DRAINAGE
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL F
FILTER FABRIC
RETAINED
ZONE
I
I
I
I
I
I
I
I
I
ACTIVE
ZONE
BACKDRAIN
TO70%OF
WALL HEIGHT
GRAVEL::-----L:.~..:...:!..i:!:.:...:!:ilu..l:J---
DRAINAGE FILL WALL SUBDRAIN
MIN 6" BELOW WALL
MIN 12" BEHIND UNITS I FOUNDATION SOILSI
NOTES:
1) MATERIAL GRADATION AND PLASTICITY
REINFORCED ZONE·
SIEVE SIZE % PASSING
1 INCH 100
NO. 4 2()..100
NO. 40 ()..60
NO. 200 ()..35
FOR WALL HEIGHT < 10 FEET, PLASTICITY INDEX< 20
FOR WALL HEIGHT 10 TO 20 FEET, PLASTICITY INDEX< 10
FOR TIERED WALLS, USE COMBINED WALL HEIGHTS
REAR SUBDRAIN:
4" (MIN) DIAMETER PERFORATED PVC PIPE
(SCHEDULE 40 OR EQUIVALENT) WITH
PERFORATIONS DOWN. SURROUNDED BY
1 CU. FT/FT OF 3/4" GRAVEL WRAPPED IN
FILTER FABRIC (MIRAFI 140N OR EQUIVALENT)
OUTLET SUBDRAINS EVERY 100 FEET, OR CLOSER,
BY TIGHTUNE TO SUITABLE PROTECTED OUTLET
GRAVEL DRAINAGE FILL'
SIEVE SIZE % PASSING
1 INCH 100
3/4 INCH 75-100
NO. 4 0-60
NO.40 0-50
NO. 200 ()..5
WALL DESIGNER TO REQUEST SITE-SPECIFIC CRITERIA FOR WALL HEIGHT> 20 FEET
2) CONTRACTOR TO USE SOILS WITHIN THE RETAINED AND REINFORCED ZONES THAT MEET THE STRENGTH REQUIREMENTS OF WALL DESIGN.
3) GEOGRID REINFORCEMENT TO BE DESIGNED BY WALL DESIGNER CONSIDERING INTERNAL, EXTERNAL, AND COMPOUND STABILITY.
3) GEOGRID TO BE PRETENSIONED DURING INSTALLATION.
4) IMPROVEMENTS WITHIN THE ACTIVE ZONE ARE SUSCEPTIBLE TO POST-CONSTRUCTION SETTLEMENT. ANGLE =45+ /2, WHERE IS THE
FRICTION ANGLE OF THE MATERIAL IN THE RETAINED ZONE.
5) BACKDRAIN SHOULD CONSIST OF J-DRAIN 302 (OR EQUIVALENT) OR 6-lNCH THICK DRAINAGE FILL WRAPPED IN FILTER FABRIC. PERCENT
COVERAGE OF BACKDRAIN TO BE PER GEOTECHNICAL REVIEW.
SEGMENTAL
RETAINING WALLS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL G
APPENDIX C
ASFE SHEET
Important Information about Your
Geotechnical Engineering Report
SuLJsurfacr pi oLJlen's a, e a p1111c,0J! cause of constwct1on (!elays. cost ot1e111ms cla1111s nnct ci1sp11tes
W111le /OU cannot el,m1nate ail s,1c/1 nsf...s. you can manage tnem Tl7e follo1v1no mformatwn 1~: /J10t11cfe(f to /Jelp
Gaotlcllllcll llrvlces IN Perllr■ed r.
lpeclllc ,.,.,,a~ ........ , 11111 Pro)ecll
Geotechnical engineers structure their services to meet the specific needs of
their clients. A geotechnical engineering study conducted tor a civil engi-
neer may not fulfill the needs of a construction contractor or even another
civil engineer. Because each geotechnical engineering study is unique, r.:ich
geotechnical engineering report is unique, preparprl solely tor the client. No
one except you should rely on your geotechnica1 engineering report without
first conferring with the geotechnical engineer who prepared it. And no one
-not even you -should apply the report for any purpose or project
except the one originally contemplated.
ReadllllM~
Serious problems have occurred because those relying on a geotechnical
engineering report did not read it all. Do not rely on an executive summary.
Do not read selected elements only.
AGelteclacalfl~lllllladN A 1N1111 Set of Project-Flcbl'I
Geotechnical engineers consider a number of unique, project-specific fac-
tors when establishing the scope of a study. Typical factors include: the
client's goals, objectives, and risk management preferences: the general
nature of the structure involved, its size, and configuration; the location of
the structure on the site; and other planned or existing site improvements,
such as access roads, parking lots, and underground utilities. Unless the
geotechnical engineer who conducted the study specifically indicates
otherwise, do not rely on a geotechnical engineering report that was:
• not prepared for you,
• not prepared for your project,
• not prepared for the specific site explored, or
• completed before important project changes were made.
Typical changes that can erode the reliability of an existing geotechnical
engineering report include those that affect:
• the function of the proposed structure, as when it's changed from a
parking garage to an office building, or from a light industrial plant
to a refrigerated warehouse,
• elevation, configuration, location, orientation. or weight of the
proposed structure,
• composition of the design team, or
• project ownership.
As a general rule, always inform your geotechnical engineer of project
changes-even minor ones-and request an assessment of their impact.
Geotechnical engineers cannot accept responsibility or liabl'lity for problems
that occur because their reports do not consider developments of which
they were not informed.
M8uPfaca CIIIIIIIIII CIII Chlnll
A geotechnical engineering report is based on conditions that existed at the
time the study was performed. Do not rely on a geotechnical engineering
report whose adequacy may have been affected by: the passage of time; by
man-made events, such as construction on or adjacent to the site; or by
natural events, such as floods, earthquakes, or groundwater fluctuations.
Always contact the geotechnical engineer before applying the report to
determine if it is still reliable. A minor amount of additional testing or
analysis could prevent major problems.
Molt Geotachlical R11l1111 Are Profllllonal Opinions
Site exploration identifies subsurface conditions only at those points where
subsurface tests are conducted or samples are taken. Geotechnical engi-
neers review field and laboratory data and then apply their professional
judgment to render an opinion about subsurface conditions throughout the
site. Actual subsurface conditions may differ-sometimes significantly-
from those indicated in your report. Retaining the geotechnical engineer
who developed your report to provide construction observation is the
most effective method of managing the risks associated with unanticipated
conditions.
A Report's RIC8111111Bndltlm Are Not Anal
Do not overrely on the construction recommendations included in your
report. Those recommendations are not final, because geotechnical engi-
neers develop them principally from judgment and opinion. Geotechnical
engineers can finalize their recommendations only by observing actual
subsurface conditions revealed during construction. The geotechnical
engineer who developed your report cannot assume responsibility or
liability for the report's recommendations if that engineer does not perform
construction observation.
A Glltacbnlcal lillllnelrlllll 118111Pt II SUbject ta Mlllnflrlll'atltlon
Other design team members' misinterpretation of geotechnical engineering
reports has resulted in costly problems. Lower that risk by having your geo-
technical engineer confer with appropriate members of the design team alter
submitting the report. Also retain your geotechnical engineer to review perti-
nent elements of the design team's plans and specifications. Contractors can
also misinterpret a geotechnical engineering report. Reduce that risk by
having your geotechnical engineer participate in prebid and preconstruction
conferences, and by providing construction observation.
Do Nit Radrlw 1111 Dlglnear'l l.8111
Geotechnical engineers prepare final boring and testing logs based upon
their interpretation of field logs and laboratory data. To prevent errors or
omissions, the logs included in a geotechnical engineering report should
never be redrawn for inclusion in architectural or other design drawings.
Only photographic or electronic reproduction is acceptable, but recognize
that separating logs from the report can elevate risk.
Give Conb"ICtarl I COIQHtl llaplrt 1111
c.tance
Some owners and design professionals mistakenly believe they can make
contractors liable for unanticipated subsurface conditions by limiting what
they provide for bid preparation. To help prevent costly problems, give con-
tractors the complete geotechnical engineering report, but preface it with a
clearly written letter of transmittal. In that letter, advise contractors that the
report was not prepared for purposes of bid development and that the
report's accuracy is limited; encourage them to confer with the geotechnical
engineer who prepared the report (a modest fee may be required) and/or to
conduct additional study to obtain the specific types of information they
need or prefer. A prebid conference can also be valuable. Be sure contrac-
tors have sufficient time to perform additional study. Only then might you
be in a position to give contractors the best information available to you,
while requiring them to at least share some of the financial responsibilities
stemming from unanticipated conditions.
Read Responslblity Pl'avillons CIDselJ
Some clients, design professionals, and contractors do not recognize that
geotechnical engineering is far less exact than other engineering disci-
plines. This lack of understanding has created unrealistic expectations that
have led to disappointments, claims, and disputes. To help reduce the risk
of such outcomes, geotechnical engineers commonly include a variety of
explanatory provisions in their reports. Sometimes labeled "limitations'
many of these provisions indicate where geotechnical engineers' responsi-
bilities begin and end, to help others recognize their own responsibilities
and risks. Read these provisions closely. Ask questions. Your geotechnical
engineer should respond fully and frankly.
Gloanvlronnlatll Concerns Are Nol CoVINd
The equipment, techniques, and personnel used to perform a geoenviron-
mental study differ significantly from those used to perform a geotechnical
study. For that reason, a geotechnical engineering report does not usually
relate any geoenvironmental findings, conclusions, or recommendations;
e.g., about the likelihood of encountering underground storage tanks or
regulated contaminants. Unanticipated environmental problems have led to
numerous project failures. If you have not yet obtained your own geoenvi-
ronmental information, ask your geotechnical consultant for risk manage-
ment guidance. Do not rely on an environmental report prepared for
someone else.
Obtain Prollslional Alllllllce To DIii wllb Mold
Diverse strategies can be applied during building design, construction,
operation, and maintenance to prevent significant amounts of mold from
growing on indoor surfaces. To be effective, all such strategies should be
devised for the express purpose of mold prevention, integrated into a com-
prehensive plan, and executed with diligent oversight by a professional
mold prevention consultant. Because just a small amount of water or
moisture can lead to the development of severe mold infestations, a num-
ber of mold prevention strategies focus on keeping building surfaces dry.
While groundwater, water infiltration, and similar issues may have been
addressed as part of the geotechnical engineering study whose findings
are conveyed in this report, the geotechnical engineer in charge of this
project is not a mold prevention consultant; none of the sertictJs fllJf-
fonnBd In COllllflCOOII wllh the gsolBchnlcal ,,,,,,;,,ers study
Mn dBslgnBd or conducted for the purposs of mold /lffWflll-
lion. Proper /mplBmentatlon of the recommendations ca,weyfld
In tlis report wlD nut of Itself be sufflclsnt to prevent mold from
growing In or on the stroctum Involved.
Rely. ,_ A8ft-Memllll' Geotechnlcll ....
lor Adlllionll Alliltllce
Membership in ASFE/The Geoprofessional Business Association exposes
geotechnical engineers to a wide array of risk management techniques that
can be of genuine benefit for everyone involved with a construction project.
Confer with your ASFE-member geotechnical engineer for more information.
A5FE THE GEOPROFESSIONAL
BUSINESS ASSOCIATION
8811 Colesville Road/Suite G106, Silver Spring, MD 20910
Telephone: 301 /565 -2733 Facsimile: 301 /589-2017
e-mail: info@asfe.org www.asfe.org
copyright 2004 by ASFE, Inc. OuplicaUon, reproduction, or copying of this documen~ In whole or in part, by any means whatsoever, Is strictly prohibited, except with ASFE's
specific wrttten permission. Excerpting, quoting, or utherwfse extracting wording from this document Is permitted only with the express written permission of ASFE, and only for
purposes of sch<l/arly rl!S6arch or book 111view. Only members of ASFE may use this document as a complement to or as an element of a georecfl/'1/cal englnlHlring report. Any olf1M
firm, individual, or other entil'j tl18t so uses this document without being an ASFE member could be commmlng f18{Jligent or intsntional (fraudulenO misrepresentation.
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