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Geotechnical Engineering Report Union County Landfill Retaining Wall
Wingate, North Carolina
October 22, 2015
Project No. 71155054
Prepared for:
CDM Smith
Charlotte, North Carolina
Prepared by:
Terracon Consultants, Inc.
Charlotte, North Carolina
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TABLE OF CONTENTS
Page EXECUTIVE SUMMARY ............................................................................................................. i 1.0 INTRODUCTION ............................................................................................................. 1 2.0 PROJECT INFORMATION ............................................................................................. 1
2.1 Project Description ............................................................................................ 1
2.2 Site Location and Description ........................................................................... 1 3.0 SUBSURFACE CONDITIONS ........................................................................................ 2
3.1 Geology .............................................................................................................. 2
3.2 Typical Profile .................................................................................................... 2
3.3 Groundwater ...................................................................................................... 3 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ...................................... 3
4.1 Geotechnical Considerations ............................................................................ 3
4.2 Earthwork ........................................................................................................... 4
4.2.1 Site Preparation ....................................................................................... 4
4.2.2 Compaction Requirements ....................................................................... 5
4.2.3 Grading and Drainage .............................................................................. 6
4.2.4 Earthwork Construction Considerations .................................................... 6
4.2.5 Excavations .............................................................................................. 6
4.3 Foundations ....................................................................................................... 8
4.3.1 Foundation Design Recommendations ..................................................... 8
4.3.2 Foundation Construction Considerations .................................................. 8
4.4 Lateral Earth Pressures ..................................................................................... 9
4.5 Global Slope Stability ...................................................................................... 11 5.0 GENERAL COMMENTS ............................................................................................... 12
APPENDIX A – FIELD EXPLORATION
Exhibits A-1a & A-1b Site Location Map
Exhibit A-2 Boring Location Plan
Exhibit A-3 Field Exploration Description
Exhibits A-4 to A-7 Boring Logs
APPENDIX B – SUPPORTING INFORMATION
Exhibits B-1 Laboratory Testing
APPENDIX C – SUPPORTING DOCUMENTS
Exhibit C-1 General Notes
Exhibit C-2 Unified Soil Classification System
APPENDIX D – SLOPE STABILITY ANALYSIS
Exhibit D-1 Slope Stability Section Plan
Exhibit D-2 Slope Stability Section A-A’
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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EXECUTIVE SUMMARY
A geotechnical investigation has been performed for the proposed retaining wall, located at the
Union County Landfill in Wingate, North Carolina. Four (4) borings, designated B-1 through B-4
were performed to depths of approximately 15 to 28 feet below the existing ground surface in the
proposed retaining wall area.
Based on the information obtained from our subsurface exploration, the site can be developed for
the proposed project. The following geotechnical considerations were identified:
The residual soils and PWR as encountered in our borings at the site appear suitable to
support the proposed retaining wall on shallow foundations provided the subgrade is
prepared as outlined in this report.
The proposed retaining wall may be supported on conventional strip footings with a net
allowable bearing pressure of 3,000 psf for footings in residual soil. If footings are bearing
on or extended further below existing grades to PWR, a higher bearing pressure of 6,000 psf
may be used. Total and differential settlements of less than 1 inch and less than ½ inch over
40 feet or less are anticipated at these bearing pressures. Further details and
recommendations are provided herein.
The residual soils encountered at the boring locations may be excavated with conventional
construction equipment, such as bulldozers, backhoes, and trackhoes. However, difficult
excavation of very stiff to hard residual soils and partially weathered rock (PWR) may be
encountered.
We have performed a slope stability analysis at the critical section of the proposed retaining
wall alignment. Based on our analysis, the section satisfies the minimum factor of safety.
Additional details are included herein.
There are two culverts on-site that drain into the vicinity of the proposed retaining wall. These
culverts may impact design and should be accounted for by the engineer or addressed during
construction.
This summary should be used in conjunction with the entire report for design purposes. It should
be recognized that details were not included or fully developed in this section, and the report must
be read in its entirety for a comprehensive understanding of the items contained herein. The
section titled GENERAL COMMENTS should be read for an understanding of the report
limitations.
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GEOTECHNICAL ENGINEERING REPORT
UNION COUNTY LANDFILL RETAINING WALL
WINGATE, NORTH CAROLINA Project No. 71155054
October 22, 2015
1.0 INTRODUCTION
A geotechnical engineering report has been completed for the proposed retaining wall, located at
the Union County Landfill in Wingate, North Carolina. Four (4) borings, designated B-1 through B-4
were performed to depths of approximately 15 to 28 feet below the existing ground surface in the
proposed retaining wall area. Logs of the borings and a description of the field exploration, along
with a Site Location Map and Boring Location Plan are included in Appendix A of this report.
The purpose of these services is to provide information and geotechnical engineering
recommendations relative to:
subsurface soil conditions foundation design and construction
groundwater conditions lateral earth pressures
earthwork and excavations global slope stability
2.0 PROJECT INFORMATION
2.1 Project Description
ITEM DESCRIPTION
Structures New concrete retaining wall and asphalt pavement.
Surcharge loads (assumed) Traffic: 300 psf
General Site Grading Not provided, but anticipated to be close to existing grades.
Cut and fill slopes None anticipated. Temporary slopes anticipated to be maximum
3:1 (Horizontal to Vertical).
Free-standing retaining walls Concrete retaining wall. Wall estimated to be 9.3 feet high and
approximately 170-feet long.
Below Grade Areas None anticipated.
2.2 Site Location and Description
ITEM DESCRIPTION
Location This project is located at the Union County Landfill located at 2125
Austin Chaney Road in Wingate, NC.
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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ITEM DESCRIPTION
Existing development The property includes an existing parking area, multiple buildings,
and waste disposal areas adjacent to an existing retaining wall.
Current ground cover Manicured grass areas, trees, and asphalt parking and drive areas.
Existing topography
The site is relatively flat in the vicinity of the asphalt parking and
access drive areas. The site appears to slope down approximately
8-feet for the waste disposal containers adjacent to the existing
retaining wall.
3.0 SUBSURFACE CONDITIONS
3.1 Geology
The project site is located in the Piedmont Physiographic Province, an area underlain by ancient
igneous and metamorphic rocks. The residual soils in this area are the product of in-place
chemical weathering of rock. The typical residual soil profile consists of clayey soils near the
surface where soil weathering is more advanced, underlain by sandy silts and silty sands that
generally become harder with depth to the top of parent bedrock. Alluvial soils are typically present
within floodplain areas along creeks and rivers in the Piedmont. According to the 1985 Geologic
Map of North Carolina, the site is within the Carolina Slate Belt. The bedrock underlying the site
generally consists of Cid Formation Metamudstone and Meta-Argillite, which is described as thin to
thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone,
metaconglomerate, and metavolcanic rock.
The boundary between soil and rock in the Piedmont is not sharply defined. A transitional zone
termed “partially weathered rock” is normally found overlying the parent bedrock. Partially
weathered rock is defined for engineering purposes as residual material with a standard
penetration test resistance exceeding 100 blows per foot. The transition between hard/dense
residual soils and partially weathered rock occurs at irregular depths due to variations in degree of
weathering. Groundwater is typically present in fractures within the partially weathered rock or
underlying bedrock in upland areas of the Piedmont. Fluctuations in groundwater levels on the
order of 2 to 4 feet are typical in residual soils and partially weathered rock in the Piedmont,
depending on variations in precipitation, evaporation, and surface water runoff. Seasonal high
groundwater levels are expected to occur during or just after the typically cooler months of the year
(November through April).
3.2 Typical Profile
Based on the results of the borings, subsurface conditions on the project site can be generalized
as follows:
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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Surficial materials encountered in the borings included approximately 3 to 5 inches of topsoil or
stone. Below the surficial materials, residual soils were encountered in each of our borings,
except B-4, to depths ranging from approximately 3 to 5.5 feet below existing grades. Residual
soils encountered consisted of sandy silt. This soil visually classifies as ML in accordance with
the Unified Soil Classification System (USCS). Standard penetration test values (N-values) in
the sandy silt ranged from 29 to 73 blows per foot (bpf), indicating a very stiff to hard
consistency.
Partially weathered rock (PWR) was encountered in borings B-1 to B-3 below the residual soils,
and below the surficial materials in boring B-4. The PWR was sampled and visually classified as
sandy silt. Auger refusal was encountered in each boring at depths ranging from approximately 15
to 28 feet below existing grades.
Conditions encountered at each boring location are indicated on the individual boring logs.
Stratification boundaries on the boring logs represent the approximate location of changes in soil
types; in-situ, the transition between materials may be gradual. Details for each of the borings can
be found on the boring logs in Appendix A of this report.
3.3 Groundwater
The boreholes were observed during and after completion of drilling for the presence and level of
groundwater. Groundwater was not encountered in any of the borings. Each borehole was
immediately backfilled after drilling, making subsequent groundwater measurements
unobtainable.
It should be recognized that fluctuations of the groundwater table will occur due to seasonal
variations in the amount of rainfall, runoff and other factors not evident at the time the borings were
performed. Therefore, groundwater levels during construction or at other times in the life of the
structure may be higher or lower than the levels indicated on the boring logs. The possibility of
groundwater level fluctuations should be considered when developing the design and construction
plans for the project.
4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION
4.1 Geotechnical Considerations
In our opinion, the residual soils and PWR as encountered in our borings at the site are suitable
to support the proposed retaining wall on shallow foundations provided the subgrade is
prepared as outlined in this report. We recommend close examination of the bearing materials be
performed during construction to confirm stable soil conditions.
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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The residual soils encountered at the boring locations may be excavated with conventional
construction equipment, such as bulldozers, backhoes, and trackhoes. However, difficult
excavation of very stiff to hard residual soils and partially weathered rock (PWR) may be
encountered. We recommend that the contractor submit unit rates for difficult excavations in their
bid. Additional information regarding difficult excavation is included herein.
The proposed site retaining wall was evaluated for global slope stability. The slope stability
analysis was performed at a critical section of the proposed retaining wall alignment. Based on our
analysis, the section satisfies the minimum factor of safety. Additional details are included herein.
It should be noted that during site drilling operations, it was observed that there are two culverts
that drain into the vicinity of the proposed retaining wall. While not part of our scope of
services, these culverts may impact design and should be accounted for by the engineer or
addressed during construction.
4.2 Earthwork
4.2.1 Site Preparation
Existing vegetation, topsoil and any otherwise unsuitable material should be removed from the
construction areas prior to placing fill. Existing utilities should be removed and relocated, or
abandoned in place and filled with concrete or grout. The exposed subgrade soils in areas to
receive fill or at the subgrade elevation in cut areas should be proofrolled to detect soft or loose
soils and other unsuitable materials that may be present. Proofrolling should be performed with
a moderately loaded, tandem axle dump truck or similar pneumatic-tired construction equipment
weighing approximately 10 to 15 tons in the proposed building areas. A Terracon representative
should observe this operation to aid in delineating unstable soil areas. Proofrolling should be
performed after a suitable period of dry weather to avoid degrading an otherwise acceptable
subgrade. Soils which continue to rut or deflect excessively under the proofrolling operations
should be remediated as recommended by the geotechnical engineer.
If subgrade soils are unsuitable, they will require removal and replacement; however, if they are
unstable due to excessive moisture, the most economical solution for remediation may be to
scarify, dry and recompact the material. This remediation is most effective during the typically
hotter months of the year (May to October). If construction is performed during the cooler period
Based on the results of our subsurface exploration, it is our opinion that the proposed retaining
wall may be supported on conventional strip footings with net allowable bearing pressures of
3,000 psf in residual soils. If footings are bearing on or extended further below existing grades to
PWR, a higher bearing pressure of 6,000 psf may be used. Total and differential settlements of
less than 1 inch and less than ½ inch over 40 feet or less are anticipated at these bearing pres-
sures, if subgrade soils are prepared as described in this report. Further details and recommen-
dations are provided herein.
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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of the year, the timeline for scarifying, drying, and recompacting typically increases considerably
and may lead to alternative remediation solutions. These solutions can include overexcavation
of some or all of the unstable material to be backfilled with either approved engineered fill or
ABC Stone. Potential undercutting can be reduced if the site preparation work is performed
during a period of dry weather and if construction traffic is kept to a minimum on prepared
subgrades. We recommend that the contractor submit a unit rate cost for undercutting as part of
the bidding process.
The existing soils encountered in our borings appear to be suitable for re-use as engineered fill.
Engineered fill should meet the following material property requirements:
Fill Type 1 USCS Classification Acceptable Location for Placement
On-site Soils ML
(LL < 50 & PI < 30) All locations and elevations
Imported Low-Plasticity
Soils
ML, CL, SC, SM
(LL < 50 & PI < 20 with a
minimum 15% passing No.
200 sieve)
All locations and elevations
1. Controlled, compacted fill should consist of approved materials that are free of organic matter and
debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A
sample of each material type should be submitted to the geotechnical engineer for evaluation.
4.2.2 Compaction Requirements
We recommend that engineered fill be tested for moisture content and compaction during
placement. Should the results of the in-place density tests indicate the specified moisture or
compaction limits have not been met, the area represented by the test should be reworked and
retested as required until the specified moisture and compaction requirements are achieved.
Engineered fill should meet the following compaction requirements:
ITEM DESCRIPTION
Fill Lift Thickness
8 to 10 inches or less in loose thickness when
heavy, self-propelled compaction equipment is
used
4 to 6 inches in loose thickness when hand-
guided equipment (e.g. jumping jack or plate
compactor) is used
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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ITEM DESCRIPTION
Minimum Compaction Requirements
95% of the materials maximum standard Proctor
dry density (ASTM D 698)
The upper 12 inches in pavement and building
areas should be compacted to at least 100% of
the materials maximum standard Proctor dry
density (ASTM D 698)
Moisture Content Requirements
Within 3% of the optimum moisture content value
as determined by the standard Proctor test at the
time of placement and compaction
4.2.3 Grading and Drainage
Final surrounding grades should be sloped away from the retaining wall on all sides to prevent
ponding of water. It should be noted that during site drilling operations, it was observed that
there are two culverts that drain into the vicinity of the proposed retaining wall. While not part of
our scope of services, these culverts may impact design and should be accounted for by the
engineer or addressed during construction.
4.2.4 Earthwork Construction Considerations
Unstable subgrade conditions could develop during general construction operations, particularly if
the soils are wetted and/or subjected to repetitive construction traffic. The use of light construction
equipment would aid in reducing subgrade disturbance. Should unstable subgrade conditions
develop, stabilization measures will need to be employed.
Upon completion of filling and grading, care should be taken to maintain the subgrade moisture
content prior to construction of on-grade slab and pavements. Construction traffic over the
completed subgrade should be avoided to the extent practical. The site should also be graded
to prevent ponding of surface water on the prepared subgrades or in excavations. If the
subgrade should become frozen, desiccated, saturated, or disturbed, the affected material
should be removed or these materials should be scarified, moisture conditioned, and
recompacted prior to on-grade slab and pavement construction.
The geotechnical engineer should be retained during the construction phase of the project to
observe earthwork and to perform necessary tests and observations during subgrade
preparation and just prior to construction of building slabs and pavements.
4.2.5 Excavations
The residual and fill soils encountered at the boring locations may be excavated with
conventional construction equipment, such as bulldozers, backhoes, and trackhoes; however,
very dense/hard residual soils and PWR were encountered at relatively shallow depths in each
of the borings. Additionally, auger refusal was encountered in each of the borings at depths
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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ranging from approximately 15 to 28 feet below existing grades. Shallow PWR and bedrock
material may also be encountered between boring locations. Smaller equipment may have
difficulty excavating PWR. A larger trackhoe or bulldozer equipped with a single-tooth ripper
may be required to excavate these materials. Some PWR, especially in confined excavations,
and rock will require blasting or impact hammering to efficiently excavate. We recommend that
unit rates for mass rock and trench rock be included in the bid package to limit disputes, in the
case that rock-like materials are encountered.
PWR may be encountered during site development. The depth and thickness of PWR,
boulders, and rock lenses or seams can vary dramatically in short distances and between the
testing locations.
It is our opinion that a clear and appropriate definition of rock be included in the project
specifications to reduce the potential for misunderstandings. A sample definition of rock for
excavation specifications is provided below:
Mass Rock is defined as any material that cannot be dislodged by a Caterpillar
D-8 Bulldozer, or equivalent, equipped with a single tooth ripper, without the use
of impact hammers or drilling and blasting. Trench Rock is defined as any
material that cannot be dislodged by a Caterpillar 312 hydraulic backhoe, or
equivalent, without the use of impact hammers or drilling and blasting. Boulders
or masses of rock exceeding ½ or ¼ cubic yard in volume shall also be
considered mass or trench rock, respectively, during excavation. These
classifications do not include materials such as loose rock, concrete, or other
materials that can be removed by means other than impact hammering, but
which for any reason, such as economic reasons, the Contractor chooses to
remove by impact hammering.
As a minimum, all temporary excavations should be sloped or braced as required by
Occupational Safety and Health Administration (OSHA) regulations to provide stability and safe
working conditions. Temporary excavations may be required during grading operations. The
grading contractor should be responsible for designing and constructing stable, temporary
excavations and should shore, slope or bench the sides of the excavations as required, to
maintain stability of both the excavation sides and bottom. All excavations should comply with
applicable local, state and federal safety regulations, including the current OSHA Excavation
and Trench Safety Standards.
Construction site safety is the sole responsibility of the contractor who controls the means,
methods and sequencing of construction operations. Under no circumstances shall the
information provided herein be interpreted to mean that Terracon is assuming any responsibility
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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for construction site safety or the contractor's activities; such responsibility shall neither be implied
nor inferred.
4.3 Foundations
In our opinion, the proposed retaining wall can be supported by shallow, strip footing foundation
systems bearing within suitable residual soils and PWR or new properly compacted fill. Design
recommendations for shallow foundations for the proposed structure are presented in the
following sections.
4.3.1 Foundation Design Recommendations
DESCRIPTION Wall
Net allowable bearing pressure 1 3,000 psf (residual soil) / 6,000 psf (PWR)
Minimum dimensions 24 inches
Minimum embedment below finished grade 18 inches
Approximate total settlement < 1 inch
Approximate differential settlement < 1/2 inch over 40 feet
1. The recommended net allowable bearing pressure is the pressure in excess of the minimum
surrounding overburden pressure at the footing base elevation. Assumes any fill or soft soils, if
encountered, will be undercut and replaced with engineered fill.
4.3.2 Foundation Construction Considerations
The foundation bearing materials should be evaluated at the time of the foundation excavation.
A representative of Terracon should use a combination of hand auger borings and dynamic
cone penetrometer (DCP) testing in conjunction with visual observations to determine the
suitability of the bearing materials for the design bearing pressure.
The base of all foundation excavations should be free of water and loose soil and rock prior to
placing concrete. Concrete should be placed soon after excavating to reduce bearing soil
disturbance. Should the soils at bearing level become disturbed, saturated, or frozen, the
affected soil should be removed prior to placing concrete. Exposure to inclement weather can
introduce unwanted moisture into the footing subgrade. If construction occurs during inclement
weather, and concreting of foundations is not possible at the time they are excavated, a layer of
lean concrete should be placed on exposed bearing surfaces for protection. Where high
moisture conditions are encountered at footing bearing elevations, the bottom of the
excavations could be stabilized with a relatively clean, well-graded crushed stone or gravel, or a
lean concrete mud mat to provide a working base for construction.
If unsuitable bearing soils are encountered in footing excavations, the excavations should be
extended deeper to suitable soils. The footings could bear directly on the soils at the lower level
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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or on lean concrete backfill placed in the excavations. The footings could also bear on properly
compacted structural fill extending down to the suitable soils. Overexcavation for compacted
structural fill placement below footings should extend laterally beyond all edges of the footings
at least 8 inches per foot of overexcavation depth below footing base elevation. The
overexcavation should then be backfilled up to the footing base elevation with well-graded
granular material placed in lifts of 10 inches or less in loose thickness and compacted to at least
98 percent of the material's maximum standard Proctor dry density (ASTM D-698). The
overexcavation and backfill procedures are described in the following figure.
4.4 Lateral Earth Pressures
Reinforced concrete walls with unbalanced backfill levels on opposite sides should be designed
for earth pressures at least equal to those indicated in the following table. Earth pressures will
be influenced by structural design of the walls, conditions of wall restraint, methods of
construction and/or compaction and the strength of the materials being restrained. Two wall
restraint conditions are shown. Active earth pressure is commonly used for design of
free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition
assumes no wall movement. The recommended design lateral earth pressures do not include a
factor of safety and do not provide for possible hydrostatic pressure on the walls.
D = Depth of overexcavation to suitable soils, as determined by a Terracon representative during construction.
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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Earth Pressure Coefficients
Earth
Pressure
Conditions
Earth Pressure Coefficient for
Backfill Type
Equivalent
Fluid Density
(pcf)
Surcharge
Pressure,
p1 (psf)
Earth
Pressure,
p2 (psf)
Active
(Ka)
On-site soils – 0.36
Imported granular soils – 0.33
43
40
(0.36)S
(0.33)S
(43)H
(40)H
At-Rest
(Ko)
On-site soils – 0.53
Imported granular soils – 0.50
64
60
(0.53)S
(0.50)S
(64)H
(60)H
Passive
(Kp)
On-site soils – 2.77
Imported granular soils – 3.00
360
360 --- ---
Applicable conditions to the above include:
For active earth pressure, wall must rotate about base, with top lateral movements of
about 0.002 H to 0.004 H, where H is wall height
For passive earth pressure to develop, wall must move horizontally to mobilize
resistance
Uniform surcharge, where S is surcharge pressure
In-situ soil backfill weight a maximum of 120 pcf
Horizontal backfill, compacted to 95 percent of standard Proctor maximum dry density
Unit weight of water (ɣw) is 62.4 pcf
Loading from heavy compaction equipment not included
No hydrostatic pressures acting on wall
No dynamic loading
No safety factor included in soil parameters
Ignore passive pressure in the upper 24 inches
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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Backfill placed against structures should consist of granular soils or low plasticity cohesive soils.
For the granular values to be valid, the granular backfill must extend out from the base of the
wall at an angle of at least 45 and 60 degrees from vertical for the active/at-rest and passive
cases, respectively. High plasticity clay (CH) and elastic silt (MH) should not be used as
backfill.
To minimize the build-up of lateral soil pressures in excess of the recommended design
pressures, over-compaction of the fill behind the wall should be avoided; however, a lesser
degree of compaction may permit excessive post-construction settlements. In order to limit wall
pressures resulting from over-compaction of wall backfill, we recommend that backfill within 5
feet of a wall be compacted by small, hand-operated compaction equipment to 95 percent of the
standard Proctor maximum dry density. Remaining backfill should be compacted in accordance
with the compaction recommendations provided in the Earthwork section of this report.
4.5 Global Slope Stability
A slope stability analysis for the proposed retaining wall was performed at the cross section of
the critical section of the retaining wall, i.e., the area along the wall alignment having the lowest
existing elevation and potential for the wall to be at its tallest. The location of the critical section
performed in our analysis is shown on Exhibit D-1 in Appendix D. The section selected for the
slope stability analysis is based on our understanding of the proposed retaining wall, the
existing topographic information provided by CDM Smith, and the borings that were completed
along the proposed retaining wall alignment.
The SLOPE/W computer program developed by Geo-Slope, Inc. was used for the slope stability
analysis. The design parameters used in the analysis were based on the findings during our
field exploration, laboratory testing results, literature research with regard to soil strength
conditions, and our experience with similar soils in the project area. Please refer to the following
table for the material strength parameters utilized for the slope stability analysis.
Soil Strength Parameters
Material
Effective Stress
Total Unit Weight (pcf) c’
(psf)
’
(Degrees)
Fill Soils 0 28 115
Residual Soils 100 26 115
PWR 0 45 135
The failure surface with the minimum factor of safety for the soil strength parameters tabulated
above is presented on Exhibit D-2 in Appendix D. The computer-generated outputs include the
cross-section analyzed along with the failure surface representing the minimum factor of safety,
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
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the center of the circle of that failure surface, and the entry and exit points of the failure surfaces
that were analyzed. The minimum factor of safety for the section was determined to be greater
than 2.3. It is our opinion that this factor of safety is sufficient for the proposed retaining wall
under the conditions analyzed.
5.0 GENERAL COMMENTS
Terracon should be retained to review the final design plans and specifications so comments
can be made regarding interpretation and implementation of our geotechnical recommendations
in the design and specifications. Terracon also should be retained to provide observation and
testing services during grading, excavation, foundation construction and other earth-related
construction phases of the project.
The analysis and recommendations presented in this report are based upon the data obtained
from the borings performed at the indicated locations and from other information discussed in
this report. This report does not reflect variations that may occur between borings, across the
site, or due to the modifying effects of construction or weather. The nature and extent of such
variations may not become evident until during or after construction. If variations appear, we
should be immediately notified so that further evaluation and supplemental recommendations
can be provided.
The scope of services for this project does not include either specifically or by implication any
environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or
prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the
potential for such contamination or pollution, other studies should be undertaken.
This report has been prepared for the exclusive use of our client for specific application to the
project discussed and has been prepared in accordance with generally accepted geotechnical
engineering practices. No warranties, either express or implied, are intended or made. Site
safety, excavation support, and dewatering requirements are the responsibility of others. In the
event that changes in the nature, design, or location of the project as outlined in this report are
planned, the conclusions and recommendations contained in this report shall not be considered
valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this
report in writing.
APPENDIX A
FIELD EXPLORATION
TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY
QUADRANGLES INCLUDE: WATSON, NC (1/1/1987).
SITE LOCATION MAP
Union County Landfill Retaining Wall 2125 Austin Chaney Road
Wingate, NC DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION
PURPOSES
KCM
CRB
CRB
CRB
A1 & A2
10/22/15
A-1a
Exhibit
2020-E Starita Road
Charlotte, NC 28206
71155054 Project Manager:
Drawn by:
Checked by: Approved by:
Project No.
File Name: Date:
1”=24,000 SF Scale:
PROVIDED BY MICROSOFT BING MAPS SITE LOCATION MAP
Union County Landfill Retaining Wall 2125 Austin Chaney Road
Wingate, NC
2020-E Starita Road
Charlotte, NC 28206
71155054
DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION
PURPOSES
Project Manager:
Drawn by:
Checked by: Approved by:
KCM
CRB
CRB
CRB
A1 & A2
10/22/15
Project No.
File Name: Date:
A-1b
Exhibit
AS SHOWN Scale:
BORING LOCATION PLAN
10/22/15
2020-E Starita Road
Charlotte, NC 28206
71155054 AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS
LEGEND:
= Approximate Location of Borings
Union County Landfill Retaining Wall 2125 Austin Chaney Road
Wingate, NC DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION
PURPOSES
Project Manager:
Drawn by:
Checked by: Approved by:
KCM
CRB
B-1
CRB
CRB
B-2
A1 & A2
B-3
B-4
Scale:
Project No.
File Name: Date:
AS SHOWN A-2
Exhibit
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
Exhibit A-3
Field Exploration Description
The boring locations were laid out on the site by Terracon personnel and were measured from
available site features. Right angles for the boring locations were estimated. The locations of the
borings should be considered accurate only to the degree implied by the means and methods used
to define them.
The borings were drilled with an ATV-mounted rotary drill rig using hollow stem augers to advance
the boreholes. Samples of the soil encountered in the borings were obtained using the split-barrel
sampling procedure.
In the split barrel sampling procedure, the number of blows required to advance a standard 2
inch O.D. split barrel sampler the last 12 inches of the typical total 18 inch penetration by means
of a 140 pound hammer with a free fall of 30 inches, is the standard penetration resistance
value (SPT-N). This value is used to estimate the in-situ relative density of cohesionless soils
and consistency of cohesive soils.
An automatic SPT hammer was used to advance the split-barrel sampler in the borings
performed on this site. A significantly greater efficiency is achieved with the automatic hammer
compared to the conventional safety hammer operated with a cathead and rope. This higher
efficiency has an appreciable effect on the SPT-N value. The effect of the automatic hammer's
efficiency has been considered in the interpretation and analysis of the subsurface information
for this report.
The samples were tagged for identification, sealed to reduce moisture loss, and taken to our
laboratory for further examination, testing, and classification. Information provided on the boring
logs attached to this report includes soil descriptions, consistency evaluations, boring depths,
sampling intervals, and groundwater conditions. The borings were backfilled with auger cuttings
prior to the drill crew leaving the site.
A field log of each boring was prepared by a staff professional. These logs included visual
classifications of the materials encountered during drilling as well as the driller’s interpretation of
the subsurface conditions between samples. Final boring logs included with this report represent
the engineer's interpretation of the field logs and include modifications based on laboratory
observation and tests of the samples.
6713 37-27-1016
8
12
2
4
00
13-30-43N=73
34-50/4"
35-50/6"
50/2"
50/4"
50/1"50/0"
0.3
3.0
18.519.0
4" TOPSOILSANDY SILT (ML), light brown to brown with tan, white, red, and black,hard, residuum
PARTIALLY WEATHERED ROCK, sampled as light brown to brown withtan, white, red, and black sandy silt with rock fragments
NO RECOVERYAuger Refusal at 19 Feet
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.
GR
AP
HIC
LO
G
TH
IS B
OR
ING
LO
G IS
NO
T V
ALI
D IF
SE
PA
RA
TE
D F
RO
M O
RIG
INA
L R
EP
OR
T.
G
EO
SM
AR
T L
OG
-NO
WE
LL 7
115
505
4 -
BO
RIN
G L
OG
S.G
PJ
TE
RR
AC
ON
2015
.GD
T 1
0/2
2/1
5
Union County Landfill Wingate, North CarolinaSITE:
Page 1 of 1
Advancement Method:Hollow Stem Augers
Abandonment Method:Borings backfilled with soil cuttings upon completion.
2020-E Starita RoadCharlotte, North Carolina
Notes:
Project No.: 71155054
Drill Rig: CME-550X
Boring Started: 9/30/2015
BORING LOG NO. B-1CDM SmithCLIENT:Charlotte, North Carolina
Driller: J. Cain
Boring Completed: 9/30/2015
Exhibit: A-4
See Exhibit A-3 for description of fieldprocedures.See Appendix B for description of laboratoryprocedures and additional data (if any).
See Appendix C for explanation of symbols andabbreviations.
PROJECT: Union County Landfill Retaining Wall
PE
RC
EN
T F
INE
S
WA
TE
RC
ON
TE
NT
(%
)
ATTERBERGLIMITS
LL-PL-PI
SA
MP
LE T
YP
E
WA
TE
R L
EV
EL
OB
SE
RV
AT
ION
S
DE
PT
H (
Ft.)
5
10
15
RE
CO
VE
RY
(In
.)
FIE
LD T
ES
TR
ES
ULT
S
DEPTH
LOCATION See Exhibit A-2
Dry Cave-In
No Free Water Observed
Dry Cave-In
WATER LEVEL OBSERVATIONSNo Free Water Observed
612
5
2
4
1
1
0
7-12-17N=29
50/5"
50/2"
50/4"
50/1"
50/1"
50/0"
0.4
3.0
17.5
20.5
5" TOPSOIL / STONESANDY SILT (ML), light brown to brown with tan, white, red, and black, verystiff, residuum
PARTIALLY WEATHERED ROCK, sampled as light brown to brown withtan, white, red, and black sandy silt with rock fragments
PARTIALLY WEATHERED ROCK, sampled as very light brown to very lightgray sandy silt with rock fragments
Auger Refusal at 20.5 Feet
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.
GR
AP
HIC
LO
G
TH
IS B
OR
ING
LO
G IS
NO
T V
ALI
D IF
SE
PA
RA
TE
D F
RO
M O
RIG
INA
L R
EP
OR
T.
G
EO
SM
AR
T L
OG
-NO
WE
LL 7
115
505
4 -
BO
RIN
G L
OG
S.G
PJ
TE
RR
AC
ON
2015
.GD
T 1
0/2
2/1
5
Union County Landfill Wingate, North CarolinaSITE:
Page 1 of 1
Advancement Method:Hollow Stem Augers
Abandonment Method:Borings backfilled with soil cuttings upon completion.
2020-E Starita RoadCharlotte, North Carolina
Notes:
Project No.: 71155054
Drill Rig: CME-550X
Boring Started: 9/30/2015
BORING LOG NO. B-2CDM SmithCLIENT:Charlotte, North Carolina
Driller: J. Cain
Boring Completed: 9/30/2015
Exhibit: A-5
See Exhibit A-3 for description of fieldprocedures.See Appendix B for description of laboratoryprocedures and additional data (if any).
See Appendix C for explanation of symbols andabbreviations.
PROJECT: Union County Landfill Retaining Wall
PE
RC
EN
T F
INE
S
WA
TE
RC
ON
TE
NT
(%
)
ATTERBERGLIMITS
LL-PL-PI
SA
MP
LE T
YP
E
WA
TE
R L
EV
EL
OB
SE
RV
AT
ION
S
DE
PT
H (
Ft.)
5
10
15
20
RE
CO
VE
RY
(In
.)
FIE
LD T
ES
TR
ES
ULT
S
DEPTH
LOCATION See Exhibit A-2
Dry Cave-In
No Free Water Observed
Dry Cave-In
WATER LEVEL OBSERVATIONSNo Free Water Observed
548
23
35-27-88
18
8
4
3
1
1
1
11-13-16N=29
11-16-20N=36
30-50/2"
50/4"
50/3"
50/1"
50/1"
50/1"
0.3
5.5
22.0
27.0
28.1
3" TOPSOILSANDY SILT (ML), trace gravel, light brown to brown with red and tan, verystiff to hard, residuum
PARTIALLY WEATHERED ROCK, sampled as light brown to brown withtan, white, and red sandy silt
PARTIALLY WEATHERED ROCK, sampled as very light brown to very lightgray sandy silt with rock fragments
PARTIALLY WEATHERED ROCK, sampled as very light gray sandy siltwith rock fragmentsAuger Refusal at 28.1 Feet
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.
GR
AP
HIC
LO
G
TH
IS B
OR
ING
LO
G IS
NO
T V
ALI
D IF
SE
PA
RA
TE
D F
RO
M O
RIG
INA
L R
EP
OR
T.
G
EO
SM
AR
T L
OG
-NO
WE
LL 7
115
505
4 -
BO
RIN
G L
OG
S.G
PJ
TE
RR
AC
ON
2015
.GD
T 1
0/2
2/1
5
Union County Landfill Wingate, North CarolinaSITE:
Page 1 of 1
Advancement Method:Hollow Stem Augers
Abandonment Method:Borings backfilled with soil cuttings upon completion.
2020-E Starita RoadCharlotte, North Carolina
Notes:
Project No.: 71155054
Drill Rig: CME-550X
Boring Started: 9/30/2015
BORING LOG NO. B-3CDM SmithCLIENT:Charlotte, North Carolina
Driller: J. Cain
Boring Completed: 9/30/2015
Exhibit: A-6
See Exhibit A-3 for description of fieldprocedures.See Appendix B for description of laboratoryprocedures and additional data (if any).
See Appendix C for explanation of symbols andabbreviations.
PROJECT: Union County Landfill Retaining Wall
PE
RC
EN
T F
INE
S
WA
TE
RC
ON
TE
NT
(%
)
ATTERBERGLIMITS
LL-PL-PI
SA
MP
LE T
YP
E
WA
TE
R L
EV
EL
OB
SE
RV
AT
ION
S
DE
PT
H (
Ft.)
5
10
15
20
25
RE
CO
VE
RY
(In
.)
FIE
LD T
ES
TR
ES
ULT
S
DEPTH
LOCATION See Exhibit A-2
Dry Cave-In
No Free Water Observed
Dry Cave-In
WATER LEVEL OBSERVATIONSNo Free Water Observed
3
2
2
5
1
0
50/3"
50/2"
50/2"
50/5"
50/1"
50/0"
0.3
15.0
4" STONEPARTIALLY WEATHERED ROCK, sampled as light brown and brown tovery light gray sandy silt with rock fragments
Auger Refusal at 15 Feet
Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.
GR
AP
HIC
LO
G
TH
IS B
OR
ING
LO
G IS
NO
T V
ALI
D IF
SE
PA
RA
TE
D F
RO
M O
RIG
INA
L R
EP
OR
T.
G
EO
SM
AR
T L
OG
-NO
WE
LL 7
115
505
4 -
BO
RIN
G L
OG
S.G
PJ
TE
RR
AC
ON
2015
.GD
T 1
0/2
2/1
5
Union County Landfill Wingate, North CarolinaSITE:
Page 1 of 1
Advancement Method:Hollow Stem Augers
Abandonment Method:Borings backfilled with soil cuttings upon completion.
2020-E Starita RoadCharlotte, North Carolina
Notes:
Project No.: 71155054
Drill Rig: CME-550X
Boring Started: 9/30/2015
BORING LOG NO. B-4CDM SmithCLIENT:Charlotte, North Carolina
Driller: J. Cain
Boring Completed: 9/30/2015
Exhibit: A-7
See Exhibit A-3 for description of fieldprocedures.See Appendix B for description of laboratoryprocedures and additional data (if any).
See Appendix C for explanation of symbols andabbreviations.
PROJECT: Union County Landfill Retaining Wall
PE
RC
EN
T F
INE
S
WA
TE
RC
ON
TE
NT
(%
)
ATTERBERGLIMITS
LL-PL-PI
SA
MP
LE T
YP
E
WA
TE
R L
EV
EL
OB
SE
RV
AT
ION
S
DE
PT
H (
Ft.)
5
10
15
RE
CO
VE
RY
(In
.)
FIE
LD T
ES
TR
ES
ULT
S
DEPTH
LOCATION See Exhibit A-2
Dry Cave-In
No Free Water Observed
Dry Cave-In
WATER LEVEL OBSERVATIONSNo Free Water Observed
APPENDIX B
LABORATORY TESTING
Geotechnical Engineering Report Union County Landfill Retaining Wall ■ Wingate, North Carolina October 22, 2015 ■ Terracon Project No. 71155054
Exhibit B-1
Laboratory Testing
Samples retrieved during the field exploration were taken to the laboratory for further
observation by the project geotechnical engineer and were classified in accordance with the
Unified Soil Classification System (USCS) described in Appendix A. At that time, the field
descriptions were confirmed or modified as necessary. Moisture content, Atterberg Limits, and
wash no. 200 sieve tests were conducted in general accordance with the applicable ASTM
standards on selected soil samples and the test results are presented on the boring logs.
Laboratory tests were conducted on selected soil samples. The laboratory test results were
used for the geotechnical engineering analyses, and the development of earthwork and lateral
earth pressure recommendations. Laboratory tests were performed in general accordance with
the applicable ASTM, local or other accepted standards.
Selected soil samples obtained from the site were tested for the following engineering
properties:
In-situ Water Content
Sieve Analysis
Atterberg Limits
Descriptive classifications of the soils indicated on the boring logs are in accordance with the
enclosed General Notes and the Unified Soil Classification System. Also shown are estimated
Unified Soil Classification Symbols. A brief description of this classification system is included
in Appendix C of this report. All classification was by visual manual procedures. Selected
samples were further classified using the results of Material Finer than No. 200 Sieve and
Atterberg limits testing. The Water Content, Material Finer than No. 200 Sieve and Atterberg
limits test results are provided on the boring logs.
The following table summarizes the in-situ moisture content, wash No. 200 sieve tests, and
Atterberg Limits test results. These results are also shown on the boring logs in Appendix A.
Sample
Location
Depth,
(feet)
In-situ
Moisture
Content,
(%)
% Passing
the No. 200
Sieve
Liquid
Limit, (%)
Plastic
Limit, (%)
Plasticity
Index, (%)
B-1 1.0 – 2.5 13 67 37 27 10
B-2 1.0 – 2.5 6 - - - -
B-3 1.0 – 2.5 8 54 35 27 8
B-3 3.5 – 5.0 23 - - - -
APPENDIX C
SUPPORTING DOCUMENTS
Exhibit: C-1
Unconfined Compressive StrengthQu, (psf)
500 to 1,000
2,000 to 4,000
4,000 to 8,000
1,000 to 2,000
less than 500
> 8,000
Non-plasticLowMediumHigh
DESCRIPTION OF SYMBOLS AND ABBREVIATIONSS
AM
PL
ING
WA
TE
R L
EV
EL
FIE
LD
TE
ST
S
GENERAL NOTES
Over 12 in. (300 mm)12 in. to 3 in. (300mm to 75mm)3 in. to #4 sieve (75mm to 4.75 mm)#4 to #200 sieve (4.75mm to 0.075mmPassing #200 sieve (0.075mm)
Particle Size
< 55 - 12> 12
Percent ofDry Weight
Descriptive Term(s)of other constituents
RELATIVE PROPORTIONS OF FINES
01 - 1011 - 30
> 30
Plasticity Index
Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dryweight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils haveless than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, andsilts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may beadded according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are definedon the basis of their in-place relative density and fine-grained soils on the basis of their consistency.
LOCATION AND ELEVATION NOTES
Percent ofDry Weight
Major Componentof Sample
TraceWithModifier
RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY
TraceWithModifier
DESCRIPTIVE SOIL CLASSIFICATION
BouldersCobblesGravelSandSilt or Clay
Descriptive Term(s)of other constituents
N
(HP)
(T)
(DCP)
(PID)
(OVA)
< 1515 - 29> 30
Term
PLASTICITY DESCRIPTION
Water levels indicated on the soil boringlogs are the levels measured in theborehole at the times indicated.Groundwater level variations will occurover time. In low permeability soils,accurate determination of groundwaterlevels is not possible with short termwater level observations.
Water Level Aftera Specified Period of Time
Water Level After aSpecified Period of Time
Water InitiallyEncountered
StandardPenetrationTest
Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracyof such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey wasconducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographicmaps of the area.
Standard Penetration TestResistance (Blows/Ft.)
Hand Penetrometer
Torvane
Dynamic Cone Penetrometer
Photo-Ionization Detector
Organic Vapor Analyzer
ST
RE
NG
TH
TE
RM
S Standard Penetration orN-Value
Blows/Ft.
Descriptive Term(Consistency)
Descriptive Term(Density)
CONSISTENCY OF FINE-GRAINED SOILS
(50% or more passing the No. 200 sieve.)Consistency determined by laboratory shear strength testing, field
visual-manual procedures or standard penetration resistance
Standard Penetration orN-Value
Blows/Ft.
(More than 50% retained on No. 200 sieve.)Density determined by Standard Penetration Resistance
RELATIVE DENSITY OF COARSE-GRAINED SOILS
Hard > 30
> 50 15 - 30Very Stiff
Stiff
Medium Stiff
Very Soft 0 - 1
Medium Dense
SoftLoose
Very Dense
8 - 1530 - 50Dense
4 - 810 - 29
2 - 44 - 9
Very Loose 0 - 3
Exhibit C-2
UNIFIED SOIL CLASSIFICATION SYSTEM
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A
Soil Classification
Group
Symbol Group Name B
Coarse Grained Soils:
More than 50% retained
on No. 200 sieve
Gravels:
More than 50% of
coarse fraction retained
on No. 4 sieve
Clean Gravels:
Less than 5% fines C
Cu 4 and 1 Cc 3 E GW Well-graded gravel F
Cu 4 and/or 1 Cc 3 E GP Poorly graded gravel F
Gravels with Fines:
More than 12% fines C
Fines classify as ML or MH GM Silty gravel F,G,H
Fines classify as CL or CH GC Clayey gravel F,G,H
Sands:
50% or more of coarse
fraction passes No. 4
sieve
Clean Sands:
Less than 5% fines D
Cu 6 and 1 Cc 3 E SW Well-graded sand I
Cu 6 and/or 1 Cc 3 E SP Poorly graded sand I
Sands with Fines:
More than 12% fines D
Fines classify as ML or MH SM Silty sand G,H,I
Fines classify as CL or CH SC Clayey sand G,H,I
Fine-Grained Soils:
50% or more passes the
No. 200 sieve
Silts and Clays:
Liquid limit less than 50
Inorganic: PI 7 and plots on or above “A” line J CL Lean clay K,L,M
PI 4 or plots below “A” line J ML Silt K,L,M
Organic: Liquid limit - oven dried
0.75 OL Organic clay K,L,M,N
Liquid limit - not dried Organic silt K,L,M,O
Silts and Clays:
Liquid limit 50 or more
Inorganic: PI plots on or above “A” line CH Fat clay K,L,M
PI plots below “A” line MH Elastic Silt K,L,M
Organic: Liquid limit - oven dried
0.75 OH Organic clay K,L,M,P
Liquid limit - not dried Organic silt K,L,M,Q
Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat
A Based on the material passing the 3-inch (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles
or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded
gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly
graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded
sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded
sand with silt, SP-SC poorly graded sand with clay
E Cu = D60/D10 Cc =
6010
2
30
DxD
)(D
F If soil contains 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.
H If fines are organic, add “with organic fines” to group name. I If soil contains 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,”
whichever is predominant. L If soil contains 30% plus No. 200 predominantly sand, add “sandy” to
group name. M If soil contains 30% plus No. 200, predominantly gravel, add
“gravelly” to group name. N PI 4 and plots on or above “A” line. O PI 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line.
APPENDIX D
SLOPE STABILITY ANALYSIS
LEGEND:
= Approximate Location of Slope Stability Analysis
= Approximate Location of Soil Test Borings
SLOPE STABILITY SECTION PLAN
Union County Landfill Retaining Wall
2125 Austin Chaney Road
Wingate, NCD-1
71155054
10/22/2015
CRB
KCM
CRB
DJC
AS SHOWN
Project Manager:
Drawn by:
Checked by:
Approved by:
Project No.
Scale:
File Name:
Date:
EXHIBIT
D-1 SSSPDIAGRAM IS FOR GENERAL LOCATION
ONLY, AND IS NOT INTENDED FOR
CONSTRUCTION PURPOSES2020 Starita Road, Suite E Charlotte, North Carolina 28206
PH. (704) 509-1777 FAX. (704) 509-1888
A’
A
B-2
B-4
B-3
B-1
D-2
71155054
10/22/2015
CRB
KCM
CRB
DJC
AS SHOWN
Project Manager:
Drawn by:
Checked by:
Approved by:
Project No.
Scale:
File Name:
Date:
EXHIBIT
D-2 A-A’DIAGRAM IS FOR GENERAL LOCATION
ONLY, AND IS NOT INTENDED FOR
CONSTRUCTION PURPOSES2020 Starita Road, Suite E Charlotte, North Carolina 28206
PH. (704) 509-1777 FAX. (704) 509-1888
SLOPE STABILITY SECTION A-A’
Union County Landfill Retaining Wall
2125 Austin Chaney Road
Wingate, NC
Center of Failure Surface
Minimum Factor of Safety
Traffic Surcharge = 300 psf
Note: Slope/W computer software
developed by GeoStudio was utilized in
our analysis.
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