SW3181002_Soils Report_20190116

ECS Southeast, LLP
Geotechnical Engineering Report
Waxhaw-Indian Trail Subdivision

Indian Trail, Union County, North Carolina

ECS Project Number 08:12249

June 23, 2017

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ECS Project No. 08:12249 Page 2
EXECUTIVE SUMMARY
This report contains the results of our preliminary subsurface exploration for the proposed single-
family development with two stormwater ponds located along Waxhaw Indian Trail Road in
Indian Trail, North Carolina. ECS has assumed that the maximum column and wall loads for the
structures will not exceed 100 kips and 4 kips per linear foot, respectively. Construction is
expected to include the stripping/grubbing, mass grading, new underground utilities, onsite
stormwater ponds, and paved parking/drive areas.

Organic laden soils approximately 3 to 4 inches thick were encountered at the existing ground
surface at each of the boring locations. Fill soils were encountered in Borings B-2, B-3, B-5, B-6,
and B-7, and extended to depths ranging from approximately 3 to 8 feet below the ground
surface. Residual soils were encountered below the fill soils in boring locations B-2, B-3, B-5, B-6,
and B-7, and beneath the surficial soils at boring locations B-1, B-4, B-8, B-9, B-10, B-11, and B-12,
and extended to depths ranging from approximately 3 to 20 feet below the ground surface. The
fill soils consisted mainly of Sandy Silt (ML) and Elastic Silt (MH). The residual soils typically
consisted of Sandy SILT (ML), Elastic SILT (MH), and Sandy CLAY (CL). Partially Weathered Rock
(PWR) was encountered below the surficial material at boring location B-1, and below the residual
soils at the remaining boring locations at depths ranging from 3 to 12 feet below the ground
surface.

Specific information regarding the preliminary subsurface exploration procedures and the site and
subsurface conditions at the time of our exploration are discussed in detail in the subsequent
sections of this report. Please note this Executive Summary is an important part of this report but
should be considered a “summary” only. The subsequent sections of this report constitute our
findings, conclusions, and recommendations in their entirety. Furthermore, ECS should review
our findings and recommendations in their entirety once the final project criteria have been
established.

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1.0 INTRODUCTION
1.1 GENERAL
The purpose of this study was to provide preliminary subsurface conditions at the site and to
evaluate those conditions with regard to foundation and floor slab support, along with general
site development. The project will include the construction of wood-framed single-family
residences with slab-on-grades and associated surface parking and drive areas. Two stormwater
ponds are also anticipated at the project site.

The preliminary recommendations developed for this report are based on project information
supplied by RHH Land Investors, LLC. This report contains the results of our preliminary
subsurface exploration and laboratory testing programs, site characterization, engineering
analyses, and recommendations for the design and construction of the proposed structures.

1.2 SCOPE OF SERVICES

To obtain the necessary geotechnical information required for design of the proposed building,
twelve (12) widely spaced soil test borings were performed at locations selected by ECS. These
borings were located within the proposed building footprints, associated parking/drive areas, and
stormwater pond areas. A laboratory-testing program was also implemented to characterize the
physical and engineering properties of the subsurface soils.

This report discusses our exploratory and testing procedures, presents our findings and
evaluations and includes the following.

• Information on site conditions including geologic information and special site features.
• Description of the field exploration and laboratory tests performed.
• Final logs of the soil borings and records of the field exploration and laboratory tests in
accordance with the standard practice of geotechnical engineers. This includes a boring
location diagram and vicinity map.
• Measurement of the surficial materials at each boring location and notation of this
information on the boring logs and in the text of the report. ECS can provide approximate
grade elevation for the top of borings if a relevant topography survey is provided.
• Preliminary geotechnical recommendations regarding site suitability for proposed
development.
• Evaluation of the on-site soil characteristics encountered in the soil borings. Specifically,
we will discuss the suitability of the on-site materials for reuse as engineered fill to
support ground slabs and pavements. A discussion of groundwater, in-place fill, rock, and
alluvial soils (if discovered) and their potential impact on structures and project
construction will be provided.

1.3 AUTHORIZATION
Our services were provided in accordance with our Proposal No. 08:20748P, dated March 28,
2017, as authorized by Mr. Bryant Spencer with RHH Land Investors, LLC on May 22, 2017, and
includes the Terms and Conditions of Service outlined with our Proposal.

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2.0 PROJECT INFORMATION
2.1 PROJECT LOCATION
The site is located along Waxhaw Indian Trail Road in Indian Trail, North Carolina as shown in the
Site Vicinity Map (Figure 2.1.1) below, and included in the Appendix.

Figure 2.1.1. Site Location

2.2 CURRENT SITE CONDITIONS
The site is moderately wooded on the western portion of the site and lightly wooded on the
southern and eastern portions of the site. Based on the historical imagery from Google Earth, it
appears that the site was developed to its current state since before 1993.

Based on the Google Earth topographic data, the ground surface at the site generally ranges from
a high elevation of approximately 713 feet in the eastern portion of the site to a low elevation of
approximately 650 feet on the western portion of the site.

2.3 PROPOSED CONSTRUCTION
We understand that the project will include the construction of wood-framed single-family
residences with slab on grades and associated surface parking and drive areas. Two stormwater
ponds are also anticipated at the project site. No site retaining walls are anticipated at this time.

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2.3.1 Structural Information/Loads

The following information explains our understanding of the structures and their anticipated
loads:

Table 2.3.1.1 Design Values
SUBJECT DESIGN INFORMATION / EXPECTATIONS
# of Stories 1 to 2 stories above grade
Usage Residential
Framing We anticipate that the buildings will be slab on grade with
wood-framing.
Column Loads 100 kips maximum (estimated)
Wall Loads 4 kips per linear foot (klf) maximum (estimated)

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3.0 FIELD EXPLORATION
3.1 FIELD EXPLORATION PROGRAM
The field exploration was planned with the objective of characterizing the project site in general
geotechnical and geological terms and to evaluate subsequent field and laboratory data to assist
in the determination of geotechnical recommendations.

3.1.1 Test Borings

The subsurface conditions were explored by drilling seven (7) widely spaced soil test borings (B-1
through B-7) within the building pads, two (2) soil test borings in stormwater ponds (B-8 and B-9),
and three (3) soil test borings in pavement areas (B-10 through B-12). A track-mounted Diedrich
D50 drill rig was utilized to drill the soil test borings. Borings were generally advanced to depths
ranging from approximately 10 to 20 feet below the current ground surface.

Boring locations were identified in the field by ECS personnel using handheld GPS techniques and
existing landmarks as reference prior to mobilization of our drilling equipment. The approximate
as-drilled boring locations are shown on the Boring Location Diagram in Appendix A. Ground
surface elevations noted on our boring logs were estimated from the provided topographic plan
and should be considered accurate only to the degree implied by the method used to obtain
them.

Standard penetration tests (SPTs) were conducted in the borings at regular intervals in general
accordance with ASTM D 1586. Small representative samples were obtained during these tests
and were used to classify the soils encountered. The standard penetration resistances obtained
provide a general indication of soil shear strength and compressibility

3.2 REGIONAL/SITE GEOLOGY
The site is located in the Piedmont Physiographic Province of North Carolina. The native soils in
the Piedmont Province consist mainly of residuum with underlying saprolites weathered from the
parent bedrock, which can be found in both weathered and unweathered states. Although the
surficial materials normally retain the structure of the original parent bedrock, they typically have
a much lower density and exhibit strengths and other engineering properties typical of soil. In a
mature weathering profile of the Piedmont Province, the soils are generally found to be finer
grained at the surface where more extensive weathering has occurred. The particle size of the
soils generally becomes more granular with increasing depth and gradually changes first to
weathered and finally to unweathered parent bedrock. The mineral composition of the parent
rock and the environment in which weathering occurs largely control the resulting soil's
engineering characteristics. The residual soils are the product of the weathering of the parent
bedrock.

In addition, it is apparent that the natural geology across the site has been modified in the past by
grading that included the placement of fill materials. The quality of man-made fills can vary
significantly, and it is often difficult to assess the engineering properties of existing fills.
Furthermore, there is no specific correlation between N-values from standard penetration tests
performed in soil test borings and the degree of compaction of existing fill soils; however, a

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qualitative assessment of existing fills can sometimes be made based on the N-values obtained
and observations of the materials sampled in the test borings.

3.3 SUBSURFACE CHARACTERIZATION
The following sections provide generalized characterizations of the soil and rock strata
encountered during our subsurface exploration. For subsurface information at a specific location,
refer to the Boring Logs in Appendix B.

Table 3.3.1 Subsurface Stratigraphy
Approximate
Depth Range
(ft)
Approximate
Average
Elevation (ft)
Stratum Description Ranges of
SPT(1) N-values
(bpf)
0 to 1
(Surface
Cover)
702-665 I Varying amounts of surficial organic laden soil was
present at the ground surface at each of the boring
locations.
N/A
1 to 5.5 690-673 II FILL –Medium Stiff to Very Stiff, Elastic SILT (MH),
Red, Moist(2)
7 to 24
5.5 to 14 675-660 III RESIDUAL –Stiff to Hard, Sandy SILT (ML), Tan to Red,
Moist
14 to 38
14 to 20 683-653 IV PWR-Partially Weathered Rock samples as Sandy
SILT (ML)(3)
100+
Notes: (1) Standard Penetration Test
(2) Fill soils encountered at boring locations B-2, B-3, B-5, B-6, and B-7.
(3) Partially Weathered Rock encountered at boring locations B-1, B-2, B-4, B-7, B-8, and B-12

3.4 GROUNDWATER OBSERVATIONS
Groundwater measurements were attempted at the termination of drilling and prior to
demobilization from the site. Each of the boring locations was dry at the time of drilling and to
the depths explored. Cave-in depths were attempted to be measured at each of the boring
locations with cave-in depths ranging from approximately 6.1 to 25.5 feet. Cave-in of a soil test
boring can be caused by groundwater hydrostatic pressure, weak soil layers, and/or drilling
activities (i.e. drilling fluid circulation or advancement of bit).

Fluctuations in the groundwater elevation should be expected depending on precipitation, run-
off, utility leaks, and other factors not evident at the time of our evaluation. Normally, highest
groundwater levels occur in late winter and spring and the lowest levels occur in late summer and
fall. Depending on time of construction, groundwater may be encountered at shallower depths
and locations not explored during this study. If encountered during construction, engineering
personnel from our office should be notified immediately.

3.5 SEASONAL HIGH WATER TABLE
A licensed soil scientist was onsite during the drilling of the potential stormwater pond borings (B-
8 and B-9) in order to determine the depth of the seasonal high water table (SHWT). The
characteristics of the soil were observed, including texture, depth, slope, the presence in

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ECS Project No. 08:12249 Page 8
accordance with current soil science practices and technology. The results of the SHWT study are
included in the Appendix of this report.

SOURCE:

GOOGLE EARTH
2016

NOT TO SCALE
FIGURE 1
SEASONAL HIGH WATER TABLE BORING MAP
WAXHAW-INDIAN TRAIL SUBDIVISION
INDIAN TRAIL, NORTH CAROLINA

ECS PROJECT NO. 49:4641
LEGEND

= Boring Location
SHWT Boring - 18
SHWT B-8
SHWT B-9
N

APPENDIX B – Field Operations

Reference Notes for Boring Logs
Boring Logs B-1 through B-12

Reference Notes for Boring Logs (FINAL 08-23-2016).doc © 2016 ECS Corporate Services, LLC. All Rights Reserved
COHESIVE SILTS & CLAYS
UNCONFINED
COMPRESSIVE
STRENGTH, QP
4
SPT5
(BPF)
CONSISTENCY7
(COHESIVE)
<0.25 <3 Very Soft
0.25 - <0.50 3 - 4 Soft
0.50 - <1.00 5 - 8 Medium Stiff
1.00 - <2.00 9 - 15 Stiff
2.00 - <4.00 16 - 30 Very Stiff
4.00 - 8.00 31 - 50 Hard
>8.00 >50 Very Hard

GRAVELS, SANDS & NON-COHESIVE SILTS
SPT5 DENSITY
<5 Very Loose
5 - 10 Loose
11 - 30 Medium Dense
31 - 50 Dense
>50 Very Dense

REFERENCE NOTES FOR BORING LOGS

1Classifications and symbols per ASTM D 2488-09 (Visual-Manual Procedure) unless noted otherwise.
2To be consistent with general practice, “POORLY GRADED” has been removed from GP, GP-GM, GP-GC, SP, SP-SM, SP-SC soil types on the boring logs.
3Non-ASTM designations are included in soil descriptions and symbols along with ASTM symbol [Ex: (SM-FILL)].
4Typically estimated via pocket penetrometer or Torvane shear test and expressed in tons per square foot (tsf).
5Standard Penetration Test (SPT) refers to the number of hammer blows (blow count) of a 140 lb. hammer falling 30 inches on a 2 inch OD split spoon sampler
required to drive the sampler 12 inches (ASTM D 1586). “N-value” is another term for “blow count” and is expressed in blows per foot (bpf).
6The water levels are those levels actually measured in the borehole at the times indicated by the symbol. The measurements are relatively reliable
when augering, without adding fluids, in granular soils. In clay and cohesive silts, the determination of water levels may require several days for the
water level to stabilize. In such cases, additional methods of measurement are generally employed.
7Minor deviation from ASTM D 2488-09.

RELATIVE
AMOUNT7
COARSE
GRAINED
(%)
FINE
GRAINED
(%)
Trace <5 <5
Dual Symbol
(ex: SW-SM)
10 10
With 15 - 20 15-25
Adjective
(ex: “Silty”)
25 - <50 30 - <50
WATER LEVELS6
WL Water Level (WS)(WD)
(WS) While Sampling
(WD) While Drilling
SHW Seasonal High WT
ACR After Casing Removal
SWT Stabilized Water Table
DCI Dry Cave-In
WCI Wet Cave-In
DRILLING SAMPLING SYMBOLS & ABBREVIATIONS
SS Split Spoon Sampler PM Pressuremeter Test
ST Shelby Tube Sampler RD Rock Bit Drilling
WS Wash Sample RC Rock Core, NX, BX, AX
BS Bulk Sample of Cuttings REC Rock Sample Recovery %
PA Power Auger (no sample) RQD Rock Quality Designation %
HSA Hollow Stem Auger
PARTICLE SIZE IDENTIFICATION
DESIGNATION PARTICLE SIZES
Boulders 12 inches (300 mm) or larger
Cobbles 3 inches to 12 inches (75 mm to 300 mm)
Gravel: Coarse ¾ inch to 3 inches (19 mm to 75 mm)
Fine 4.75 mm to 19 mm (No. 4 sieve to ¾ inch)
Sand: Coarse 2.00 mm to 4.75 mm (No. 10 to No. 4 sieve)
Medium 0.425 mm to 2.00 mm (No. 40 to No. 10 sieve)
Fine 0.074 mm to 0.425 mm (No. 200 to No. 40 sieve)
Silt & Clay (“Fines”) <0.074 mm (smaller than a No. 200 sieve)
MATERIAL1,2
ASPHALT
CONCRETE
GRAVEL
TOPSOIL
VOID
BRICK
AGGREGATE BASE COURSE
FILL3 MAN-PLACED SOILS
GW WELL-GRADED GRAVEL
gravel-sand mixtures, little or no fines
GP POORLY-GRADED GRAVEL
gravel-sand mixtures, little or no fines
GM SILTY GRAVEL
gravel-sand-silt mixtures
GC CLAYEY GRAVEL
gravel-sand-clay mixtures
SW WELL-GRADED SAND
gravelly sand, little or no fines
SP POORLY-GRADED SAND
gravelly sand, little or no fines
SM SILTY SAND
sand-silt mixtures
SC CLAYEY SAND
sand-clay mixtures
ML SILT
non-plastic to medium plasticity
MH ELASTIC SILT
high plasticity
CL LEAN CLAY
low to medium plasticity
CH FAT CLAY
high plasticity
OL ORGANIC SILT or CLAY
non-plastic to low plasticity
OH ORGANIC SILT or CLAY
high plasticity
PT PEAT
highly organic soils
B-1B-2B-3S-2 3.50 - 5.00 26.9B-4B-5S-1 1.00 - 2.50 18.4 ML 44 27 17B-6B-7B-8S-1 1.00 - 2.50 23.2B-9B-10S-1 1.00 - 2.50 30.7 MH 57 33 24B-11B-12S-1 1.00 - 2.50 21.4Laboratory Testing SummaryNotes:1. ASTM D 2216, 2. ASTM D 2487, 3. ASTM D 4318, 4. ASTM D 1140, 5. See test reports for test method, 6. See test reports for test methodDefinitions:MC: Moisture Content, Soil Type: USCS (Unified Soil Classification System), LL: Liquid Limit, PL: Plastic Limit, PI: Plasticity Index, CBR: California Bearing Ratio, OC: Organic Content (ASTM D 2974)Project No. 08:12249Project Name: Waxhaw-Indian Trail Subdivision - GEOPM: Josh BradshawPE: Lee J. McGuinnessPrinted On: Friday, June 23, 2017SampleSourceSampleNumberDepth(feet)MC1(%)SoilType2LLAtterberg Limits3PL PIPercentPassingNo. 200Sieve4MaximumDensity(pcf)Moisture - Density (Corr.)5OptimumMoisture(%)CBRValue6OtherPage 1 of 1