SW3210301_Soils Report (Geotechnical)_20210309

REPORT OF GEOTECHNICAL SUBSURFACE EXPLORATION
CRESSWIND
POTTER ROAD
UNION COUNTY, NORTH CAROLINA
SUMMIT PROJECT NO. 2409.02
Prepared For:
Mr. Travis Manning
Kolter Homes, LLC
8913 Silver Springs Court
Charlotte, North Carolina 28215
Email: [e-mail]
Prepared By:
SUMMITEngineering, Laboratory & Testing, P. C. (SUMMIT)
3575 Centre Circle Drive
Fort Mill, South Carolina29715
May 17, 2019

May 17, 2019
Mr. Travis Manning
Kolter Homes, LLC
8913 Silver Springs Court
Charlotte, North Carolina 28215
Email: [e-mail]
Subject:Report of Geotechnical Subsurface Exploration
Cresswind
Potter Road
Union County, North Carolina
SUMMIT Project No. 2409.02
Dear Mr. Manning:
SUMMITEngineering, Laboratory & Testing, P. C. (SUMMIT) has completed a geotechnical
subsurface explorationfor the Cresswindsitelocatedoff of Potter Road in Union County, North
Carolina.These geotechnical services were performed in general accordance with our Proposal
No. P2019-504-G, dated April 14, 2019. This report contains a brief description of the project
information provided to us, general site and subsurface conditions revealed during our
geotechnical subsurface exploration and our general recommendations regarding foundation
design and construction.
SUMMITappreciates the opportunity to be of service to you on this project. If you have any
questions concerning the information presented herein or if we can be of further assistance, please
feel free to call us at [phone].
Sincerely yours,
SUMMITEngineering, Laboratory & Testing, P. C.
Todd A. Costner, E.I. Kerry C. Cooper, P.E.
Senior Professional Senior Geotechnical Engineer
i

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
TABLE OF CONTENTS
SECTIONPage
EXECUTIVE SUMMARY...........................................................................................................iii
1.0INTRODUCTION..............................................................................................................1
1.1.Site and Project Description....................................................................................1
1.2.Purpose of Subsurface Exploration.........................................................................1
2.0 EXPLORATION PROCEDURES......................................................................................3
2.1.Field Exploration....................................................................................................3
3.0 AREA GEOLOGY AND SUBSURFACE CONDITIONS...............................................4
3.1.Physiography and Area Geology............................................................................4
3.2.Generalized Subsurface Stratigraphy......................................................................4
3.2.1. Surface Materials........................................................................................5
3.2.2. Alluvial Soils..............................................................................................5
3.2.3. Existing Fill Soils.......................................................................................6
3.2.4. Residual Soils.............................................................................................6
3.2.5. Partially Weathered Rock and Auger Refusal............................................7
3.2.6. Groundwater Level Measurements............................................................7
4.0 EVALUATIONS AND RECOMMENDATIONS.............................................................9
4.1.General....................................................................................................................9
4.2.Shallow Foundation Recommendations.................................................................9
4.3.Retaining Wall Recommendations.......................................................................10
4.4.Low to Moderate Plasticity Moisture Sensitive Soils (MH).................................11
4.5.High Plasticity Moisture Sensitive Soils (CH).....................................................12
4.6.WetWeather Conditions.......................................................................................13
4.7.Floor Slabs............................................................................................................14
4.8.Pavements Subgrade Preparation..........................................................................14
4.9.Cut and Fill Slopes................................................................................................15
5.0 CONSTRUCTION CONSIDERATIONS........................................................................16
5.1.Abandoned Utilities/Structures.............................................................................16
5.2.Site Preparation.....................................................................................................16
5.3.Difficult Excavation..............................................................................................17
5.4.Temporary Excavation Stability...........................................................................19
5.5.Structural Fill........................................................................................................19
5.6.Suitability of Excavated Soils for Re-Use............................................................21
5.7.Engineering Services During Construction..........................................................21
6.0 RELIANCE AND QUALIFICATIONS OF REPORT....................................................23
APPENDIX 1-Figures
Site Vicinity Map.................................................................................................................1
Boring Location Plan...........................................................................................................2
APPENDIX 2 -Boring Logs
ii

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
EXECUTIVE SUMMARY
SUMMIThas completed a geotechnical subsurface explorationfor the Cresswindproject. The
purpose of this explorationwas to obtain general information regarding the subsurface conditions
and to provide geotechnical recommendations regarding foundation supportof the proposed
construction. The explorationconsisted of twenty (20) soil test borings (identified as B-1 through
B-20).The approximate test locations are shown on the Figure 2 provided in Appendix 1. The
following geotechnical engineering information was obtained as a result of the soil test borings:
Surface Materials –Surficial organic (topsoil)soils wereobservedat the existing ground
surface of the borings with thicknessesranging from approximately 2 to 6inches.
Existing Fill Soils –An approximate 6-to 8-inch layer of existing fill (disturbed) soils were
encounteredbeneath the surface materialsin all of the boringsexcept for BoringsB-2, B-13
and B-18.These existing fill soils were encountered in boringsthat were located in fields
formerly utilized for agricultural purposes;therefore, these fill soils areconsidered cultivated
soils.When sampled, the existing fill soils generally consisted of elastic silts (MH)andsandy
silts (ML).
Residual Soils -Residual (undisturbed) soils were encounteredbelow the surface materials
and/or existing fill soils and extended to either the maximum termination depth or partially
weathered rock (PWR).These residual soils generally consisted of fat clays (CH), lean clays
(CL), elastic silts (MH),andsandy silts (ML)with varying amount of rock fragments.The
Standard Penetration Resistances (SPT N-values) in theresidualsoils ranged from 4 to greater
than 50blows per foot (bpf).
Partially Weathered Rock (PWR) and Auger Refusal –Partially weathered rock (PWR)
conditions were encountered in Borings B-11, B-12, B-13, B-15, B-16 and B-20at
approximate depths ranging from 5.5 to 12feet below the existing ground surface.Auger
refusal conditions were not encountered in the borings.
Groundwater Levels -At the time of drilling, groundwater was observed in BoringsB-14 and
B-15at approximate depthsof 10 and 9feet below the existing ground surfacerespectively.
After waiting more than 24hours, water was not observed in Borings B-2, B-13 and B-18,and
water was observed in Boring B-9at adepth of 9.6feet below the existing ground surface.
Foundation Support-Based on the results of our borings, the proposed structures can be
adequately supported on shallow foundationssystemsprovided site preparation and compacted
fill recommendation procedures outlined in this report are implemented concerning unsuitable
soils such asexisting “cultivated”fill soils, fat clays, and soils with N-values less than 7 bpf.
An allowable net bearing pressure of up to 2,500pounds per square foot (psf) can be used for
design of the foundations bearing on approved undisturbed residual soils, or on structural fill
compacted to at least 95 percent of its Standard Proctor maximum dry density.
Special Construction Considerations: Special considerations are warranted concerning
existing “cultivated”fill soils,fat clays, and soils with SPT N-values less than 7 bpf.
iii

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
Dependent on final grades, the contractor can anticipate that some undercutting and/or
foundation extension may be necessary through these unsuitablesoils if encountered during
grading and construction. Should these soils be encountered during the grading and
construction activities, these soils should be evaluated in the field by a Geotechnical Engineer-
of-Record and/or his designee prior to remediation. Additional testing such as test pit
excavations and/or hand auger borings may be required in order to further evaluate these soil
conditions, depths and locations.
o Existing “Cultivated” Fill Soils:At the time of this report, no relevant information
(documentations) regarding previous grading activities, prior materials testing, and/or
geotechnical engineering services was provided for our review. Allof the borings except
for BoringsB-2, B-13and B-18encountered undocumented fill soils (fill soils not
monitored and tested during placement)and undocumented fill poses risks associated with
undetected deleterious materials within the fill soils and/or deleterious material atthe
interface between the fill soils and residual soils.
Also, based on historical aerial photographs and our site observations, agricultural fields
were present on the site. Except for Borings B-2, B-13 and B-14, all of the borings were
performed in theagricultural fields and encountered a 6-to 8-inch layer of existing fill soil
that are considered to be cultivated fill soils. Cultivated fill soil is a layer that was plowed
and disturbed for agricultural purposes. Cultivated fill soils are not suitable for building
and pavement support and are not suitable to be re-used as structural fill material due to
the organics mixed in the soil.However, if approved by the Geotechnical Engineer of
Record, the organic stained soils may be suitable as structural quality fill material if the
organic content in the soil is less than 5% and/or blended with non-organic soils to reduce
the organic content.
o Fat Clays:High plasticity and moisture sensitive (fat clays) soils were encountered beneath
the existing fill soils in BoringsB-14 and B-15toanapproximate depth of 3feet below the
existing ground surface. Highly plastic soils can undergo significant changes in volume
(shrink/swell behavior) with changes in moisture conditions. These soils typically provide
poor subgrade support for pavements and foundations.
o Soils with SPT N-values less than 7 bpf:Soils that exhibited SPT N-values less than 7 bpf
are considered not suitable to support the proposed construction.Thesesoil conditions were
generally encountered in the upper 1.5 feetof the borings.
Please note that the information provided in this executive summary is intended to be a brief
overview of project information and recommendations from the geotechnical report. The
information in the executive summary should not be used without first reading the geotechnical
report and the recommendations described therein.
iv

Report of Geotechnical ServicesSUMMITProject No. 2409.02
CresswindMay 17, 2019
1.0INTRODUCTION
1.1.Site and Project Description
The Cresswindsite is locatedoff ofPotter Roadin Union County, North Carolina.Avicinity map
showing the project’s general location is provided as Figure 1.The subject property is
approximately 162acres comprised of UnionCounty Tax Parcel IDNumbers06027007and
06009008.At the time of our field exploration, the subject site wasundeveloped landthat consisted
of mostly agricultural fields andwoodedareas.Also, Molly Branch creek waspresent along the
southern portion line and the East Fork Twelve Mill Creek waspresent along the northwestern
property line.
The Client (Kolter Homes, LLC)provided SUMMITaplan sheet titled“Concept Plan”, prepared
by Thomas & Hutton dated April 11, 2019thatindicated the configurations of the proposed
constructionplanned for this project.Based on the providedinformation, we understand the
projectis planned to include 599 single family residential lotswith associated, amenities,
pavements, roadways, utilities and storm water management systems.
At the timeof report preparation,SUMMIThadnot been provided structural details of the planned
constructionindicating proposed loads, foundation bearing elevations, orfinished floor elevations.
For this report,SUMMITassumedthe proposedstructureswill be supported on a shallow
foundation system consisting of spread, strip,and/or combined footingsand that wall loads will
be on the order of 1 to 3kips per foot.Also, grading planswerenot available at the time of this
report and we have assumed that maximum cut/fill depths will be on the order of 1 to 3feetover
the existing ground surface.
1.2.Purpose of Subsurface Exploration
The purpose of this explorationwas to obtain general geotechnical information regarding the
subsurface conditions and to provide general preliminary recommendations regarding the
geotechnical aspects of site preparation and foundation design.This report contains the following
items:
1

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
General subsurface conditions,
Boring logs and an approximate “Boring Location Plan”,
Suitable foundation types,
Allowable bearing pressuresfor design of shallow foundations,
Anticipated excavation difficulties during site grading and/or utility installation,
Remedial measures to correct unsatisfactory soil conditions during site development, as
needed,
Drainagerequirements around structures andunder floor slabs, as needed,
Construction considerations,
Pavement subgrade support guidelines.
2

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
2.0EXPLORATION PROCEDURES
2.1.FieldExploration
SUMMITvisited the site onMay 6, 7 and 8, 2019and performed a geotechnical explorationthat
consisted of twenty (20) soil test borings (identified as B-1 through B-20). Theapproximate
locationsof the borings areshown on the Figure 2 -“Boring Location Plan”providedin Appendix
1.The borings were located by professionals from our office using the provided plan, recreation-
grade handheld GPS, existing topography, and aerial maps as reference. Since the boring locations
were not surveyed, the location of the borings should be considered approximate.
The soil test borings were performed using an ATV-mounted CME 550X drill rig and extended to
approximate depths of 13.9 to 16feetbelow the existing ground surface. Hollow-stem, continuous
flight auger drilling techniques were used to advance the borings into the ground. Standard
Penetration Tests (SPT) were performed within the mechanical borings at designated intervals in
general accordance with ASTM D 1586. The SPT “N” value represents the number of blows
required to drive a split-barrel sampler 12 inches with a 140-pound hammer falling from a height
of 30 inches. When properly evaluated, the SPT results can be used as an index for estimating soil
strength and density. In conjunction with the penetration testing, representative soil samples were
obtained from each test location and returned to our laboratory for visual classification in general
accordance with ASTM D 2488.Water level measurements were attempted at the termination of
drilling. The results of these tests are presented on the individual boring logs provided in Appendix
2 at the respective test depth.
3

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
3.0AREA GEOLOGY AND SUBSURFACE CONDITIONS
3.1.Physiography and Area Geology
The subject property is located in Union County, North Carolina, which is located in the south
central Piedmont Physiographic Province. The Piedmont Province generally consists of well-
rounded hills and ridges which are dissected by a well-developedsystem of draws and streams.
The Piedmont Province is predominantly underlain by metamorphic rock (formed by heat, pressure
and/or chemical action) and igneous rock (formed directly from molten material) which were
initially formed during the Precambrian and Paleozoic eras. The volcanic and sedimentary rocks
deposited in the Piedmont Province during the Precambrian era were the host of the metamorphism
and were generally changed to gneiss and schist. The more recent Paleozoic era had periods of
igneous emplacement, with episodes of regional metamorphism resulting in the majority of the
rock types seen today.
The topographicrelief found throughoutthe Piedmont Province has developed from differential
weathering of thesesigneous and metamorphic rockformations. Ridges developed alongthe more
easily weathered and erodible rock. Because of the continued chemical and physical weathering,
the rocks in the Piedmont Province are generally covered with a mantle of soil that has weathered
in-place from the parent bedrockbelow. These soils have variable thicknesses and are referred to
as residual soils, as they are the result of in-place weathering.Residual soils aretypically fine-
grained and have a higher clay content near the ground surface because of the advanced
weathering. Similarly, residual soils typically become more coarse-grained with increasing depth
because of decreased weathering. As weathering decreaseswith depth, residual soils generally
retain the overall appearance, texture, gradation and foliations of theirparent rock.
3.2.Generalized Subsurface Stratigraphy
General subsurface conditions observedduring our geotechnical exploration are described herein.
For more detailed soil descriptions and stratifications at a particular field test location, the
respective “Boring Logs”,provided in Appendix 2 should be reviewed. The horizontal
4

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
stratification lines designating the interface between various strata represent approximate
boundaries. Transitionsbetween different strata in the field may be gradual in both the horizontal
and vertical directions.Therefore,subsurface stratigraphy between test locations may vary.
3.2.1.SurfaceMaterials
Surficial organic (topsoil)soils wereobservedin all borings at the existing ground surface
with thicknessesranging from approximately 2 to 6inches.The surficial organic soil
depths provided in this report and on the individual “Boring Logs” are based on
observations of field personnel and should be considered approximate. Please note that the
transition from surficial organic soils to underlying materials may be gradual, and therefore
the observation and measurement of the surficial organic soil depth is subjective. Actual
surficial organic soil depths should be expected to vary and generally increases with the
amount of vegetation present over the site.
Surficial Organic Soil is typically a dark-colored soil material containing roots, fibrous
matter, and/or other organic components, and is generally unsuitable for engineering
purposes. SUMMIThas not performed any laboratory testing to determine the organic
content or other horticultural properties of the observed surficial organic soils. Therefore,
the phrase “surficial organic soil” is not intended to indicate suitability for landscaping
and/or other purposes.
3.2.2.Alluvial Soils
Alluvial (water-deposited)soils were not encountered in any of the borings performed
during this exploration. Alluvial soils are typically encounteredin or near drainage
features, pond bottoms, creeksand in low-lying areas.Alluvial soils are generally loose
and/or under-compacted and, as such, are typically unsuitable for supporting the proposed
construction. Therefore, remediation may be required wherever alluvial soils are
encountered during grading activities. If these soils are encountered during sitegrading
activities,the extent of the alluvial soils should be evaluated in the field by theGeotechnical
Engineer-of-Recordor his qualified representative.Additional testing such as test pit
5

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
excavations and/or hand auger borings may be required in order to further evaluate the
alluvial soils.
3.2.3.Existing Fill Soils
An approximate 6-to 8-inch layer of existing fill (disturbed) soils were encountered
beneath the surface materials in all of the borings except for BoringsB-2, B-13 and B-18.
When sampled, the existing fill soils generally consisted of elastic silts (MH)andsandy
silts (ML).
Also, based on historical aerial photographs and our site observations, agricultural fields
were present on the site. Except for Borings B-2, B-13 and B-14, all of the borings were
performed in the agricultural fields and encountered a 6-to8-inch layer of existing fill soil
that are considered to be cultivated fill soils. Cultivated fill soil is a layer that was plowed
and disturbed for agricultural purposes. Cultivated fill soils are not suitable for building
and pavement support and are not suitable to be re-used as structural fill material due to
the organics mixed in the soil. However, if approved by the Geotechnical Engineer of
Record, the organic stained soils may be suitable as structural quality fill material if the
organic content in the soil is less than 5% and/or blended with non-organic soils to reduce
the organic content.
If fill soils are encountered at other locations in the field during construction, the fill soils
should be evaluated by the Geotechnical Engineer-of-Record, or his authorized
representative, with respect to the criteria outlined in Section 5.0–Construction
Considerations.
3.2.4.Residual Soils
Residual(undisturbed)soils were encounteredbelow the surface materials and/or existing
fill soils and extended to either the maximum termination depth or partially weathered rock
(PWR).These residual soils generally consisted of soft to very stiff fat clays (CH), firm to
very stiff lean clays (CL), firm to very stiff elastic silts (MH),and firm to very hard sandy
6

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
silts (ML)with varying amount of rock fragments.The Standard Penetration Resistances
(SPT N-values) in theresidual soils ranged from 4 to greater than 50blows per foot (bpf).
3.2.5.Partially Weathered Rockand Auger Refusal
Partially weathered rock (PWR) conditions were encountered in Borings B-11, B-12, B-
13, B-15, B-16 and B-20at approximate depths ranging from 5.5 to 12feet below the
existing ground surface.PWRis defined as soil-like material exhibiting SPT N-values in
excess of 100 bpf. When sampled, the PWR generally breaks down into sandy siltswith
rock fragments.
Auger refusal conditions were not encountered in the borings.Auger refusal is defined as
material that could not be penetrated by the drilling equipmentused during our field
exploration.
The following table summarizes the approximate depths that PWRand auger refusal
conditionswere encountered in theboringsperformed for this exploration.
SummaryTable of Partially Weathered Rockand Auger RefusalDepths
Partially Weathered RockAuger RefusalApprox. Depth,
BoringNo.
Approx. Depth,(feet)*(feet)*
B-1112---
B-125.5---
B-136 to 10---
B-158---
B-165.5---
B-2012---
*Depths were measured from the ground surface existing at the time drilling was performed.
“---“ When PWR or auger refusal conditions were not encountered in the borings.
3.2.6.Groundwater Level Measurements
At the time of drilling, groundwater was observed in Borings B-14 and B-15 at approximate
depths of 10 and 9 feet below the existing ground surface respectively. After waiting more
than 24 hours, water was not observed in Borings B-2, B-13 and B-18 and water was
7

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
observed in Boring B-9 at a depth of 9.6 feet below the existing ground surface. Please
note moisture conditions of the soil samples were noted within some of the borings and
moisture conditions within the soils may be an indication of the presence of groundwater.
Also, moist to wet soil conditions can be an indication that some manipulation (scarifying
and drying) of the soil may be required in order to obtain the specified compaction during
grading operations.
It should also be noted that groundwater levels tend to fluctuate with seasonal and climatic
variations, as well as with some types of construction operations. Therefore, water may be
encountered during construction at depths not indicated in the borings performed for this
exploration.
8

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
4.0EVALUATIONS AND RECOMMENDATIONS
4.1.General
Our preliminary evaluation and recommendations are based on the project information outlined
previously and on the data obtained from the field and laboratory testing program. If the structural
loading, geometry, or proposed building locations are changed or significantly differ from those
outlined, or if conditions are encountered during construction that differ from those encountered
by the borings, SUMMITrequests the opportunity to review our recommendations based on the
new information and make the necessary changes.
Grading plan informationwith proposed foundation bearing elevationswas not available for our
review at the time of this report. Finish grade elevations of proposedconstructionin conjunction
with the proposed foundation bearing elevationcan have a significant effect on design and
construction considerations. SUMMITshould be providedthe opportunity to review the project
grading plans prior to their finalizationwith respect to the recommendations contained in this
report.
4.2.Shallow FoundationRecommendations
Based on the results of the soil test borings,and our assumptions regarding site grading and
assumed structural building loads, theproposed structurescan be adequately supported on shallow
foundation systems provided site preparation and compacted fill recommendation procedures
outlined in this report are implemented concerning unsuitable soils such asexisting “cultivated”
fill soils, fat clays, and soils with N-values less than 7 bpf.An allowable net bearing pressure of
up to 2,500pounds per square foot (psf) can be used for design of the foundations bearing on
approved undisturbed residual soils, or on approved structural fill compacted to at least 95 percent
of its Standard Proctormaximum dry density. Please refer to section5.0 of this report for more
information.
Provided the procedures and recommendations outlinedin this report are implemented and using
the assumedloads, we have estimated a total settlement of less than 1 inch for footing design
9

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
pressures of 2,500 psf.
To avoid punching type bearing capacity failure, we recommend wall foundation widths of 18
inches or more. Exterior foundations and foundations in unheated areas should be designed to
bear at least 12 inches below finished grade for frost protection. To reduce the effects of seasonal
moisture variations in the soils, for frost protection and for bearing capacity, it is recommended
that all foundations beembedded at least 12 inches below the lowest adjacent grade.
All footing excavations and undercutting remediation operations should be evaluatedby the
Geotechnical Engineer-of-Recordor his qualifiedrepresentative to confirm that suitable soils are
present at and below the proposed bearing elevation and that the backfill operations are completed
with the recommendations of this report. This evaluation may include hand-auger and DCP testing.
If evaluation with DCP testing encounters lowerpenetration resistances than anticipated or
unsuitable materials are observed beneath the footing excavations, these bearing soilsshould be
corrected per the Geotechnical Engineer-of-Record’s recommendations.
4.3.Retaining WallRecommendations
Design Parameters for backfill properties (i.e., friction angle, earth pressure coefficients)should
use the values in the table below. These parameters are based on suitable soils with a minimum
moist unit weight of 120 pcf. SUMMITshould be retained to test the actual soils used for
construction to verify these design assumptions. To reduce long term creep or deflections to the
wall system,desirable wall backfill soils should be used. These includenon-plastic, granular soils
(sands and gravels). However,these soils may not be available on site.
Soil Parametersfor Wall Backfill
Active Passive Coefficient
Modulus of Earth Earth of Earth
Allowable
Friction Subgrade Pressure Pressure Pressure at
Bearing
Angle Reaction Coefficient Coefficient Rest
Slide
Capacity
(psf)(deg)(pci)KKpKoFriction
Backfill Type
a
2,50028° 2000.3612.770.5310.4
Residuum
o
Fill
2,500241500.4212.370.5930.4
10

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
Soils classified aselastic silts (MH) and/or fat clays (CH)shallnot be used for wall backfill or in
the retained zone as shown in Table 1610.1 of the 2015 IBC. If on-site soils are used as backfill
within the reinforced zone,the wall designer should address the need for wall drainage andthe
possibility oflong-term,time-dependent movement or creep in their design.
At the time of report preparation, we were not provided retaining wall plans or specifications.
Therefore,werequest the opportunity to review the wall plans and specifications once they are
finalized. Also, werecommendan external stability analysis (including global stability) of the
proposed wall(s) be conducted once the site layout and wall geometryis complete.
4.4.Low to Moderate Plasticity Moisture Sensitive Soils (MH)
Low to moderate plasticity and moisture sensitive (elastic silts) soils were encountered in the
majorityof the boringsperformed for this exploration.These fine-grainedsoils are susceptible to
moisture intrusion and can becomesoft when exposed to weatherand/or water infiltration.
Consequently, some undercutting and/or reworking (drying) of the near-surface soils may be
required depending upon the site management practices and weather conditions present during
construction.
Should these materials be left in-place, special consideration should be given to providing positive
drainage away from the structure and discharging roof drains a minimum of 5 feet from the
foundations to reduce infiltration of surface water to the subgrade materials.
Note: Since Low to Moderate Plasticity and Moisture Sensitive Soils can become remolded (i.e.,
softened) under the weight of repeated construction traffic and changes in moisture conditions,
thesesoils should be evaluated and closely monitored by the Geotechnical Engineer-of-Recordor
his qualified representative prior to andduring fill placement. Additional testing and inspections
of moisture sensitive soils may be warranted such aslaboratory testing, field density (compaction)
testing, hand auger borings with dynamic cone penetrometer (DCP) testing and/or test pit
excavations.
11

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
4.5.High Plasticity Moisture Sensitive Soils (CH)
High plasticity and moisture sensitive (fat clays) soils were encountered beneaththe existing fill
soils in BoringsB-14 and B-15toanapproximate depth of 3feet below the existing ground surface.
Highly plasticsoils can undergo significant changes in volume(shrink/swellbehavior) with
changes in moisture conditions. These soils typically provide poor subgrade support for
pavements and foundations.
The highly plasticmaterials encountered in the borings performed for this explorationare typically
not considered suitable for building or pavement subgradesupport. Depending on final subgrade
elevations, we recommend the highly plasticsoils be undercutfrom beneath foundations and
pavements so that the foundation elements bear on 3 feet or more of engineered fill and pavements
are supported on 1½ feet or more of engineered fill, creating a separation between the foundation
elements/pavements and the underlying highly plastic soils.
The presence of the high plasticity materialscan adversely affect the performance of the foundation
and pavement systems. Due to thepresence of highly plastic soils at the project site, we
recommend the following be implementedby the design team:
1.The high plasticity materials should be undercut from all structural and pavement areas.
The undercut subgrades should be evaluated by a staff professional upon completion of
undercut operations. Once the evaluation is completed and the subgrade appears suitable,
structural fill should be placed to subgrade elevation.
2.Three (3) feet of separation should be provided between the high plasticity materials and
foundations and one and one-half (1½) feet of separation on pavement areas. The
separation material should consist of approved structural fill materials
3.Lime stabilization techniques could be utilized in order to lower the plasticity of the
referenced soils in-place and minimize any undercut. These techniques should extend to a
depth of at least 3 feet below finished floor elevation of the building and at least 1.5 feet
on pavement areas. It should be noted that the success of lime stabilization techniques is
12

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
highly dependent upon the means and methods utilized by the contractor.
4.If the expansive soils are not undercut from beneath the structures or adequate separation
is not provided, the building foundations could be designed to either penetrate the
expansive soils or should be designed to resist the differential volume and prevent
structural damage. Slab-on-grades should be designed as structural slabs for the expansive
soils in accordance with WRI/CRSI Design of Slab-on-Ground Foundations or PTI Design
and Construction of Post-Tensioned Slabs-on-Ground.
4.6.Wet Weather Conditions
Contractors should be made aware of the moisture sensitivity of the near soils and potential
compaction difficulties.If construction is undertaken during wet weather conditions, the surficial
soils may become saturated, soft, and unworkable. The contractor can anticipate reworkingand/or
recompacting soilsmay be neededwhen excessive moisture conditions occur.Additionally,
subgrade stabilization techniques, such as chemical (lime or lime-fly ash) treatment, may be
needed to provide a more weather-resistant working surface during construction. Therefore, we
recommend that consideration be given to construction during the dryer months.
Surface runoffshould be drained away from excavations and not allowed to pond. Concrete for
foundations should be placed as soon as practical after the excavation is made. That is, the exposed
foundation soils should not be allowed to become excessively dry or wet before placement of
concrete. Bearing soilsexposed to moisture variations may become highly disturbed resulting in
the need for undercutting prior to placement ofconcrete. If excavations must remain open
overnight, or if rainfall becomes imminent whilethe bearing soils are exposed, we recommend
that a 2-to 4-inch-thick “mud-mat” of lean (2000 psi) concrete be placed on the bearing soils
before work stops for the night.
SUMMITrecommendsthat special care be given to providing adequate drainage away from the
building areas to reduce infiltration of surface water to the base course and subgrade materials. If
these materials are allowed to become saturated during the life of the slab section, a strength
13

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
reduction of the materials may result causing a reduced life of the section.
4.7.Floor Slabs
Slab-on-grade floor systems may be supported on approved residual soils, or newly compacted
fill, provided the site preparation and fill placement procedures outlined in this report are
implemented. Depending upon the amount of cuts and/or fills, unsuitable soils such as existing
fill soils, cultivated soils, fat clays,and areas which deflect, rut or pump excessively during proof-
rolling mayrequire remediation as described in Section5.2. We recommend floor slabs be isolated
from other structural components to allow independent movement of the slab and the building
foundation elements.
Immediately prior to constructing a floor slab, the areas should be proof-rolled to detect any
softened, loosened or disturbed areas that may have been exposed to wet weather or construction
traffic. Areas that are found to be disturbed or indicate pumping action during the proof-rolling
should be undercut and replaced with adequately compacted structural fill. This proof-rolling
shouldbe observed by the staff professional or a senior soils technician under his/her direction.
Proof-rolling procedures are outlined in the “Site Preparation” section of this report.
4.8.PavementsSubgrade Preparation
The pavement sections can be adequately supported on approvednon-high plasticity residual soils,
or newly compacted fill, provided the site preparation and fill placement procedures outlined in
this report are implemented. Immediately prior to constructing the pavement section, we
recommend that the areas be proofrolled to detect any softened, loosened or disturbed areas that
may have been exposed to wet weather or construction traffic. Areas that are found to be disturbed
or indicate instability during the proofrolling should be undercut and replaced with adequately
compacted structural fill or repaired as recommended by the Geotechnical Engineer. This
proofrolling should be observed by the staff professional or a senior soils technician under his/her
direction. Proofrolling procedures are outlined in the “Site Preparation” section of this report.
Due to prevalence of near surface moderate to high plasticity elastic silts and fat clays, remediation
14

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
of pavement subgrade soils may be recommended (as determined by the Geotechnical Engineer
during construction) including undercutting and replacement with additional NCDOT ABC
stone.Alternatively, lime stabilization of pavement subgrade may be a more economical option
and SUMMITcan provide lime stabilization mix design services if requested. This may be more
pronounced depending on the time of the year and seasonal conditions at the time of pavement
construction. We recommend contingency for some remediation efforts for the subgrade soils be
considered during the planning stage.
4.9.Cut and Fill Slopes
Permanent project slopes should be designed with geometry of 3 horizontal to 1 vertical or flatter.
The tops and bases of all slopes should be located 10 feet or more from structural limits and 5 feet
or more from parking limits. Fill slopes should be properly compacted according to the
recommendations provided in this report. In addition, fill slopes should be overbuilt and cut to
finished grade during construction to achieve proper compaction on the slope face. All slopes
should be seeded and maintained after construction and adhere to local, state and federal municipal
standards, if applicable.
15

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
5.0CONSTRUCTION CONSIDERATIONS
5.1.Abandoned Utilities/Structures
SUMMITrecommendsthat any existingutility linesand foundationsbe removed from within
proposed building and pavement areas.The utility backfill and foundation materialshould be
removed and the subgrade in the excavations should be evaluated by a geotechnical professional
prior to fill placement. The subgrade evaluation should consist of visual observations, probing
with a steel rod and/or performing hand auger borings with Dynamic Cone Penetrometer tests to
evaluate their suitability of receiving structural fill. Once the excavations are evaluated and
approved, they should be backfilled with adequately compacted structural fill. Excavation backfill
under proposed new foundations should consist of properly compacted structural fill, crushed
stone, flowable fillor lean concreteas approved by the Geotechnical Engineer-of-Record.
5.2.Site Preparation
Based on the results of our borings, and dependent on final grades, the contractorcan anticipate
that some undercutting and/or foundation extension through asexisting “cultivated”fill soils, fat
claysand soils with N-values less than 7 bpfmaybe required prior to building construction and/or
fill placement. If these soils are encountered during the grading activities, the extent of the
undercut required should be determined in the field by theGeotechnical Engineer-of-Record
and/or an experienced staff professional. Additional testing such as test pit excavations and/or
hand auger borings may be required in order to further evaluate these soil conditions, depths and
locations.
Topsoil, organic laden/stainedsoils,and other unsuitablematerials should be stripped/removed
fromthe proposed constructionlimits.Stripping and clearing should extend 10 feet or more
beyond the planned construction limits. Upon completion of the stripping operations, we
recommend areas planned forsupport of foundations, floor slabs, parkingareas and structural fill
be proof-rolledwith a loaded dump truck or similar pneumatic tired vehicle (minimum loaded
weight of 20 tons) under the observations of a staff professional. After excavation of the site has
16

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
been completed, the exposed subgrade in cut areas should also be proof-rolled.The proof-rolling
procedures should consist of four complete passes of the exposed areas, with two of the passes
being in a direction perpendicular to the proceeding ones. Any areas which deflect, rut or pump
excessively during proof-rolling or fail to “tighten up” after successive passes should be undercut
to suitable soils and replaced with compacted fill.
The extent of anyundercut required should be determined in the field by an experienced staff
professionalor engineerwhile monitoring constructionactivity. After the proof-rolling operation
has been completed and approved, final site grading should proceed immediately. If construction
progresses during wet weather, the proof-rolling operation should be repeatedafter any inclement
weather eventwith at least one pass in each direction immediately prior to placing fill material or
aggregate base course stone. If unstable conditions are experienced during this operation,then
undercutting or reworking of the unstable soilsmay be required.
5.3.Difficult Excavation
Based on the results of our soil test boringsand dependent on final grades, it appears that the
majority of general excavation for footings andutilities will be possible with conventional
excavating techniques. We anticipate that the residual soils can be excavated using pans, scrapers,
backhoes, and front end loaders. Depending on the location, excavations deeper than
approximately 5.5 to 12feetmay require specialized equipment and procedures.
Even though Partially Weathered Rock (PWR) conditions wereencountered in six (6) of the
boringsand auger refusal conditions were not encountered in the boringsperformed for this
exploration,thedepth and thickness of partially weathered rock, boulders,and rock lenses or seams
can vary dramaticallyinshort distances and between the boring locations; therefore, soft/hard
weathered rock, boulders or bedrock may be encountered during construction at locations or
depths, between the boring locations, not encountered during this exploration.
The table below may be used as a quick reference for rippability of in-place materials.
17

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
Summary of Rippability Based on SPT N-Values
N-Values as Shown
Descriptionof N-ValuesAnticipated Rippability
on Boring Logs
These materials maygenerally be excavated
60 < N-Value N-values lessthan 60bpfwith heavy-duty equipment such as a
Caterpillar D-8 with a single-shank ripper
N-values more than 60bpf, These materials are considered marginally
60< N-Value < 50/3”but less than 50 blows per 3 excavatable, even with heavy-duty
inches of penetrationequipment.
Blasting and/or removal with impact
N-values more than 50 blows
50/3” < N-Valuehammers istypically requiredto excavate
per 3 inches of penetration
these materials.
*This table is for general information only. Actual rippability is dependent upon many other factorsas stated
above.
Care should be exercised during excavations for footings on rock to reduce disturbance to the
foundation elevation. The bottom of each footing should be approximately level. When blasting
is utilized for foundation excavation in rock, charges should be held above design grades. Actual
grades for setting charges should be selected by the contractor and he should be responsible for
any damage caused by the blasting. All loose rock should be carefully cleaned from the bottom
of the excavation prior to pouring concrete. Footing excavations in which the rock subgrade has
been loosened due to blasting should be deepened to an acceptable bearing elevation.
In our professionalopinion,a clear and appropriate definition of rockshouldbe included in the
project specifications to reduce the potential for misunderstandings. A sample definition of rock
for excavation specifications is provided below:
Rock is defined as any material that cannot be dislodged by a Caterpillar D-8
tractor, or equivalent, equipped with a hydraulically operated power ripper (or by
a Cat 325 hydraulic backhoe, or equivalent) without the use of drilling and blasting.
Boulders or masses of rock exceeding ½ cubic yard in volume shall also be
considered rock excavation. This classificationdoes not include materials such as
loose rock, concrete, or other materials that can be removed by means other than
drilling and blasting, but which for any reason, such as economic reasons, the
Contractor chooses to remove by drilling and blasting.
18

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
5.4.Temporary Excavation Stability
Localized areas of soft or unsuitable soils not detected by our borings, or in unexplored areas, may
be encountered once grading operations begin. Vertical cuts in these soils may be unstable and
may present a significant hazard because they can fail without warning. Therefore, temporary
construction slopes greater than 5 feet in heightshould not be steeper than twohorizontal to one
vertical (2H:1V), and excavated material should not be placed within 10 feet of the crest of any
excavated slope. In addition, runoff water should be diverted away from the crest of the excavated
slopes to prevent erosion and sloughing.
Should excavations extend below final grades, shoring and bracing or flattening (laying back) of
the slopes maybe required to obtain a safe working environment. Excavation should be sloped or
shored in accordance with local, state and federal regulations, including OSHA (29 CFR Part 1926)
excavation trench safety standards.
5.5.Structural Fill
Soilto be used as structural fill should be free of organic matter, roots or other deleterious
materials. Structural fill should have aplasticity index (PI) less than 25and a liquid limit (LL)
less than 50or as approved by the Geotechnical Engineer-of-Record. Compacted structural fill
should consist of materialsclassified aseitherCL, ML, SC, SM, SP, SW, GC, GM, GP, or GW
per ASTM D-2487or as approved by the Geotechnical Engineer-of-Record. Off-site borrow soil
should also meet these same classification requirements. Non-organic, low-plasticityon-site soils
are expected to meet this criterion.However, successful reuse of the excavated, on-site soils as
compacted structural fill will depend on the moisture content of the soils encountered during
excavation. We anticipate that scarifying and drying of portions of the on-site soils will be required
before the recommended compaction can be achieved. Drying of these soils will likely result in
some delay.
All structural fill soils should be placed within the proposed structural pad and extending at least
5 feet beyond the perimeter of the pad and foundation limits.All structural fill soils should be
19

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
placed in thin (not greater than 8 inches) loose lifts and compacted to a minimum of 95 percent of
the soil's Standard Proctor maximum dry density (ASTM D 698) at/or nearoptimum moisture
content (±2%).The upper 2 feet of structural fill should be compacted to a minimum of 100
percent of the soil's Standard Proctor maximum dry density (ASTM D 698) at/ornear optimum
moisturecontent (±2%).Some manipulation of the moisture content (such as wetting, drying)
may be required during the filling operation to obtain the required degree of compaction. The
manipulation of the moisture content is highly dependent on weather conditions and site drainage
conditions. Therefore, the grading contractor should be prepared to both dry and wet the fill
materials to obtain the specified compaction during grading. Sufficient density tests should be
performed to confirm the required compaction of the fill material.
Structural Fills Greater than 10 feet Discussions:Soil undergoes both primary and secondary
consolidation (compression of the soil). Primary consolidation can take place over a short-term
during the mechanical compacting process. Secondary consolidation can take place over a long-
term and can place after the compaction process is complete and the permanent loads are in place.
The amount of secondary consolidation which can be expected increases with the depth of fill soils
and structure loads. Therefore, in order to reduce secondary consolidation, we recommend when
either mass fills or utility lines are more than 10 feet deep, the fill/backfill material below 10 feet
should be compacted to at least 98 percent of standard Proctor maximum dry density
(ASTMD698) and within 2 percentage points of the material's optimum moisture content. The
portion of the fill/backfill shallower than 10 feet should be compacted as outlined above.
Another option is to monitor the settlement with settlement plates embedded at the proposed
subgrade level. After the magnitude and rate of settlement are within acceptable levels, then
foundation and slab-on grade construction may commence. Based on our previous experience and
dependent on soil types at the site, we anticipate the time required to reduce settlements to an
acceptable level may be on the order of 30 to 90 days.
20

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
5.6.Suitabilityof Excavated Soilsfor Re-Use
Except for the fatsoils and the existing cultivated fill soils encountered during this exploration,
the soils encountered in the borings should be suitable to be used as structural fill material provided
the recommendations in this report are implemented.These soils may be utilized as non-structural
fill and backfill at landscaped or non-pavement areas of the project.We recommend non-structural
fill to be compacted to at least 92 percent of the soil’s Standard Proctor Maximum Dry Density to
reduce settlement of the fill soils particularly over utility trenches.
However, if approved by the Geotechnical Engineer-of-Record, high plasticity soils encountered
during general site grading can be mixed/blended and/or mixed with lower plasticity soils and used
as structural fill.We recommend that mixed soils be used below the top five (5)feetat deeper fill
locations and adequate drainage be provided away from structural and pavement areas. The top
five (5) feet should consist of materials classified as either CL, ML, SC, SM, SP, SW, GC, GM,
GP or GW per ASTM D-2487 or as approved by the Geotechnical Engineer-of-Record.All fill
soils should be placed in thin (not greater than 8 inches) loose lifts and compacted to a minimum
of 95 percent of the soil’s Standard Proctor maximum dry density (ASTMD698) at near optimum
moisture content (±2%).
Typically, cultivated fill soils are not suitable for building and pavement support and are not
suitable to be re-used as structural fill material due to the organics mixed in the soil. However, if
approved by the Geotechnical Engineer of Record, the organic stained soils may be suitable as
structural quality fill material if the organic content in the soil is less than 5% and/or blended with
non-organic soils to reduce the organic content.
5.7.Engineering Services During Construction
As stated previously, theengineering recommendations provided in this report are based on the
project information outlined aboveand the data obtained from field tests.However, unlike other
engineering materials like steel and concrete, the extent and properties of geologic materials (soil)
vary significantly. Regardless of the thoroughness ofa geotechnical engineering exploration, there
21

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
is always a possibility that conditions between borings will be different from those at the boring
locations, that conditions are not as anticipated by the designers, or that the construction process
has altered the subsurface conditions. This report does not reflect variations that may occur
between the boring locations. Therefore, conditions on the site may vary between the discrete
locations observed at the time of our subsurface exploration.
The nature and extent of variations between the borings may not become evident until construction
is underway. To account for this variability,professional observation, testing and monitoring of
subsurface conditions during construction should be provided as an extension of our engineering
services. These services will help in evaluating the Contractor's conformance with the plans and
specifications. Because of our unique position to understand the intent of the geotechnical
engineering recommendations, retaining us for these services will also allow us to provide
consistent service through the project construction. Geotechnical engineering construction
observations should be performed under the supervision of theGeotechnical Engineer-of-Record
from our office whois familiar with the intent of the recommendations presented herein. This
observation is recommended to evaluate whether the conditions anticipated in the design actually
exist or whether the recommendations presented herein should be modified where necessary.
Observation and testing of compacted structural fill and backfill should also be provided by our
firm.
22

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
6.0RELIANCE AND QUALIFICATIONS OF REPORT
This geotechnical subsurface explorationhas been provided for the sole use of Kolter Homes,
LLC.This geotechnical subsurface explorationshould not be relied upon by other parties without
the express written consent of SUMMITand Kolter Homes, LLC.
The analyses and recommendations submitted in this report were based, in part, on data obtained
from this exploration. If the above-described project conditions are incorrect or changed after the
issuing of this report, or subsurface conditions encountered during construction are different from
those reported, SUMMITshould be notified and these recommendations should be re-evaluated
based on the changed conditions to make appropriate revisions. We have prepared this report
according to generally accepted geotechnical engineering practices. No warranty, express or
implied, is made as to the professional advice included in this report.
23

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
APPENDIX 1–Figures

Report of Geotechnical Subsurface ExplorationSUMMITProject No. 2409.02
CresswindMay 17, 2019
APPENDIX 2–Boring Logs