SW3201003_ESHWT REPORT_20201103

Z
SUMMIT
ENGINEERING. LABORATORY. TESTING
September 24, 2020
Mr. David Algood
Auto Finance Center, LLC
11201 East Independence Boulevard
Charlotte, North Carolina 28105
Email: [e-mail]
Subject: Estimated Seasonal High Water Table (ESHWT) Determination
Union County Parcel 07102296 ESHWT
Union Beltway Road
Union County, North Carolina
SUMMIT Project No. 5918.G0799
Dear Mr. Algood:
SUMMIT Engineering, Laboratory and Testing, P. C. (SUMMIT) is pleased to submit this letter
summarizing our observations of the soil test boring as related to Estimated Seasonal High Water
Table Elevation (ESHWT) determination in the proposed BMP pond to be constructed for the
proposed project located off Union Beltway Road in Union County, North Carolina. This report
contains a brief description of the project information provided to us, general site and subsurface
conditions revealed during this exploration.
PURPOSE OF EXPLORATION
The primary purpose of this exploration was to obtain information regarding the subsurface
conditions in the proposed BMP pond, assess the engineering characteristics of the subsurface
materials, and determination of the estimated seasonal high water table mark (if evident).

Summary of ESHWT Determination
Union Countv Parcel 07102296
This report contains the following items:
• Site Vicinity Map and Boring Location Plan,
SUMMIT Project No. 5918.G0799
September 24, 2020
• Summary of Test Boring Observations, visual soil classifications and descriptions,
• A general review of the subsurface soils and estimated seasonal high water table depth
from existing ground surface (if evident),
• Groundwater level measurements.
EXPLORATION PROCEDURES
SUMMIT visited the site on September 16, 2020 to perform a soil test boring (identified as Boring
SW -I) in the proposed BMP pond. The approximate location of the boring is shown on Figure 2
— "Boring Location Plan" provided in Appendix 2. The client (Auto Finance Center, LLC)
provided SUMMIT a plan sheet titled "Sketch Plan", prepared by Yarbough-Williams & Houle,
Inc. dated June 20, 2020, that indicated the approximate location of the proposed detention pond.
The boring location was surveyed by others.
The soil test boring was performed using an ATV -mounted CME 550X drill rig and was extended
to an approximate depth of 11.3 feet below the existing ground surface. Hollow -stem, continuous
flight auger drilling techniques were used to advance the boring into the ground. Standard
Penetration Tests (SPT) were performed within the mechanical boring continuously to the
termination depth in general accordance with ASTM D 1586. 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 the test location and returned
to our laboratory for visual classification and potential laboratory testing. The soil samples
collected were visually examined and classified in general accordance with ASTM D-2488. The
Munsell Soil Color Charts (2009 Revision) were used to identify the hue, value, and chroma of
soil samples. Water level measurements were attempted at the termination of drilling. The
classification symbols are depicted on the "Boring Log" provided in Appendix 2.
2

Summary of ESHWT Determination SUMMIT Project No. 5918.G0799
Union County Parcel 07102296 September 24, 2020
GENERALIZED SUBSURFACE STRATIGRAPHY
General subsurface conditions observed during our geotechnical exploration are described herein.
For more detailed soil descriptions and stratifications at the test location, the respective "Boring
Log" provided in Appendix 2 should be reviewed. The horizontal stratification lines designating
the interface between various strata represents approximate boundaries. Transitions between
different strata in the field may be gradual in both the horizontal and vertical directions.
Beginning from the ground surface, a layer of topsoil (surficial organic soils) was observed with a
thickness of approximately 2 inches. Beneath the topsoil layer, residual (undisturbed) soils were
encountered that consisted of lean clays. Partially Weathered Rock (PWR) materials were
encountered at an approximate depth of 5.5 feet. Auger refusal material was not encountered
within the boring.
GROUNDWATER LEVEL MEASUREMENTS
At the time of drilling and after waiting more than 24 hours, groundwater was not observed in the
boring. Please note that groundwater levels tend to fluctuate with seasonal and climatic variations,
as well as with some types of construction operations.
ESTIMATED SEASONAL HIGH WATER TABLE
ESHWT is defined as the shallowest depth to a wet soil layer as a result of "true" or "permanent"
groundwater at any time during the year. The ESHWT is typically identified with a change in the
color of the soil layer due to water staining (typically, gray redoximorphic depletions and
mottling). Spots or blotches of different color or shades of color interspersed with a dominant color
in soil, commonly referred to as mottling. Mottling is a historic indication for the presence of
groundwater caused by intermittent periods of saturation and drying, and may be indicative of poor
aeration and impeded drainage. Mottling is a "general indication of groundwater" flow through
this layer, but it is not known whether the groundwater flow was recent.
3

Summary of ESHWT Determination SUMMIT Project No. 5918.G0799
Union County Parcel 07102296 September 24, 2020
CONCLUSIONS
Based on our observations, Estimated Seasonal High Water Table (ESHWT) indicators were not
evident in soils sampled in the boring. Please note that even though we did not observe ESHWT
indicators within the boring, perched water conditions can develop in soil layers above a low
permeable partially weathered rock (PWR) stratum. Perched water conditions differ from the
"true" or "permanent" water table. A perched water table is water standing above an unsaturated
zone and is often influenced by weather conditions, and occurrence of less permeable soils. Where
the ESHWT is defined as the shallowest depth to a wet soil layer as a result of "true" or
"permanent" groundwater at any time during the year. The BMP designer should take into
consideration that perched water conditions may exist above the low permeable stratum.
The following table summarizes the results of the boring and our observations.
Summary Table of the Boring Results and Our Observations
Approx.
Existing
GW Depth
Approx.
Auger
Boring
Ground
GW Depth
After
PWR
Refusal
Test
Depth
Elevation
ATD
24 Hours
Depth
Depth
Location
(Feet)'
msl 2
Feet '
Feet '
(Feet)'
(Feet)'
SW-1
11.3
688.8
NE
NE
5.5
NE
1 Depths from existing ground surface.
2msl — Mean Sea Level - Existing ground surface elevation was estimated from the provided plan
topographic information provided plan.
NE — Not Encountered in boring.
The analyses 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,
SUMMIT should 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.
4

Summary of ESHWT Determination SUMMIT Project No. 5918.G0799
Union County Parcel 07102296 September 24, 2020
CLOSING
SUMMIT appreciates the opportunity to provide our professional services for you on this project.
If you have any questions concerning the information in this proposal or if we may be of further
service, please contact us at 704.504.1717.
Sincerely,
SUMMIT ENGINEERING, LABORATORY & TESTING, P.C.
N CA&
�. r 'SUMMIT, r
Engineering, `
i Laboratory &
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= n Testing, P.C.
.
C-4361��`
Franklin D. Newsom
Staff Professional
LIST OF APPENDICES
Appendix 1 Figure No. 1 — Site Vicinity Map
Figure No. 2 — Boring Location Plan
Appendix 2 Boring Log
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Ricky O. Coker, Vf,,ky p GO
Geotechnical Enginee"i"

Summary of ESHWT Determination SUMMIT Project No. 5918.G0799
Union County Parcel 07102296 September 24, 2020
SUMMIT
ENGINEERING + LABORATORY . TESTING
APPENDIX 1
Figures

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Figure 2
Boring Location Plan Union County Parcel 07102296 ESHWT
Approx. Soil Test Boring Union Beltway Road
Location Union County, North Carolina
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Summary of ESHWT Determination SUMMIT Project No. 5918.G0799
Union County Parcel 07102296 September 24, 2020
u u I
ENGINEERING * LABORATORY * TESTING
APPENDIX 2
Boring Log

SUMMIT ENGINEERING, LABORATORY & TESTING, P.C. BORING NUMBER SW-1
CENTRE CIRCLE
FORT
FORT MILL, SOUTH CAROLINA 29715 PAGE 1 OF 1
SUMMIT 704-504-17 17
SUMMIT-COMPANIES.COM
CLIENT Auto Finance Center, LLC PROJECT NAME Union County Parcel 07102296 ESHWT
PROJECT NUMBER 5918.G0799 PROJECT LOCATION Union County North Carolina
DATE STARTED 9/16/20 COMPLETED GROUND ELEVATION 688.8 ft HOLE SIZE 6 inches
DRILLING CONTRACTOR SUMMIT GROUND WATER/CAVE-IN:
DRILLING METHOD Hollow Stem Auger AT TIME OF DRILLING -- GW NE ATD
LOGGED BY D. Robles CHECKED BY F. Newsom AT END OF DRILLING --- GW NE > 24 Hrs
NOTES See Figure 2 "Boring Location Plan" for Approx. Boring Location AFTER DRILLING ---
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♦ SPT N VALUE A
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w
0 20 40 60 80 100
1r 0-r
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0-0
MATERIAL DESCRIPTION
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0 20 40 60 80 100
J
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a_ z
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❑ FINES CONTENT (%) ❑
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of
0 20 40 60 80 100
Approx. 2" of Topsoil
(CL) RESIDUUM:
Very Stiff Pale Brown (2.5Y, 7/4) and Yellow (2.5Y, 7/8) Sandy
Lean CLAY
SPT
4-9-9-9
.........
1
(18)
................ :........ :........
----------------------------
(CL) Stiff Brownish Yellow (10YR, 6/6), Pale Brown (2.5Y, 7/4)
2.5
and Gray (10YR, 6/1) Sandy Lean CLAY with a trace of Rock
Fragments
...... .:........ :........ :........ :........
686.3
SPT
5-6-9-13
2
(15)
:........:........ . ........
(CL) Hard Brownish Yellow (10YR, 6/6), Pale Brown (2.5Y, 7/4)
and Gray (10YR, 6/1) Sandy Lean CLAY with Rock Fragments
5.0
SPT
3
8-11-20-50
(19)
....................................>.>
683.8
"
(ML) Partially Weathered Rock (PWR) when sampled becomes
Pale Brown (2.5Y, 7/4) and Very Pale Brown (10YR, 7/3) Sandy
SILT with Rock Fragments
SPT15-45-50
........ :............. ....:........ ........
4
(50/4")
»
7.5
SPT
18-32-50
'
................. ......... :........ :........
5
(50/5")
»
10.0
- -
�+ ��_
................ :........ :.................
678.8
SPT
17-33-50
6
(50/4")
»
Bottom of Boring at 11.3 feet bgs, Boring Terminated
12.5
676.3