SW3231101_Soils/Geotechnical Report_20240514

November 23, 2022
Ms. Hayden Frieslaar S U M M I T
Shea Homes r`inrP.rrRINc . ATnP' •Tr:Tir�r
A Universal E•ua1nee-lncl COrnppny
8008 Corporate Center Drive, Suite 300
Charlotte, North Carolina 28226
Email: [e-mail]
Subject: Estimated Seasonal High Water Table (ESHWT) Determinations
Underwood Road
Weddington Road
Wesley Chapel, North Carolina
SUMMIT Project No. 0109.G0046
Dear Ms. Frieslaar:
SUMMIT Engineering, Laboratory and Testing, Inc. (SUMMIT) is pleased to submit this letter
summarizing our observations of the soil test borings as related to Estimated Seasonal High
Water Table Elevation (ESHWT) determinations in the proposed stormwater BMP ponds to be
constructed for the proposed project listed above. 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 stormwater BMP ponds, assess the engineering characteristics of the
subsurface materials, and determination of the estimated seasonal high water table mark (if
evident).
3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com

Summary of ESHWT Determinations SUMMIT Project No. 0109.G0046
Underwood Road November 23, 2022
This report contains the following items:
• Site Vicinity Map and Boring Location Plan,
• 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 November 10th and 14th of 2022 and performed two (2) soil test
borings (identified as SW-16 and SW-17) in the proposed stormwater BMP ponds. The
approximate location of the borings is shown on Figure 2 — "ESHWT Boring Location Plan"
provided in Appendix 2. The client (Shea Homes) provided SUMMIT a plan sheet titled
"Underwood Road" prepared by BGE Inc., dated July 13, 2022 that indicated the approximate
locations of the proposed stormwater BMP ponds. 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. We recommend the actual boring locations be
surveyed to determine the actual boring locations and existing ground elevations.
The soil test borings were performed using an ATV-mounted CME 550X drill rig. Borings SW-16
and SW-17 were extended to an approximate depth of 8.2 and 12.6 feet below the existing
ground surface, respectively. 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 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 locations 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
3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com

Summary of ESHWT Determinations SUMMIT Project No. 0109.G0046
Underwood Road November 23, 2022
Logs" provided in Appendix 2.
GENERALIZED SUBSURFACE STRATIGRAPHY
General subsurface conditions observed during our geotechnical exploration are described
herein. For more detailed soil descriptions and stratifications at the test locations,the respective
"Boring Logs" 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 3 inches. Beneath the topsoil layer, residual (undisturbed) soils were
encountered that consisted of elastic silts (MH) and sandy silts (ML). Partially Weathered Rock
(PWR) materials were encountered in Borings SW-16 and SW-17 at approximate depths of 6 and
12 feet below the existing ground surface, respectively. Auger refusal conditions were
encountered in SW-16 and SW-17 at approximate depths of 8.2 and 12.6 feet below the existing
ground surface, respectively.
GROUNDWATER LEVEL MEASUREMENTS
At the time of drilling and after waiting more than 24 hours, groundwater was not observed in
the borings. 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.
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
3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com

Summary of ESHWT Determinations SUMMIT Project No. 0109.G0046
Underwood Road November 23, 2022
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.
CONCLUSIONS
Based on our observations, ESHWT indicators were not evident in the boring locations. Please
note that even though ESHWT indicators were not evident in the borings, perched water
conditions can develop above a low permeable material. 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 soil 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 PWR stratum.
The following table summarizes the results of the borings and our observations.
Summary Table of the Boring Results and Our Observations
Approx.
GW Depth Approx. Auger
Boring ESHWT GW Depth After PWR Refusal
Test Depth Depth ATD 24 Hours Depth Depth
Location (Feet)1 (Feet)1 (Feet)1 (Feet)1 (Feet)1 (Feet)1
SW-16 8.2 NE NE NE 6 8.2
SW-17 12.6 NE NE NE 12 12.6
1 Depths from existing ground surface.
NE — Not Encountered in boring
3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com

Summary of ESHWT Determinations SUMMIT Project No.0109.G0046
Underwood Road November 23, 2022
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.
3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com

Summary of ESHWT Determinations SUMMIT Project No. 0109.G0046
Underwood Road November 23, 2022
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, INC.
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SUMMIT
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Brian Cantrell, P.E. Adam Jordan
Geotechnical Department Manager Assistant Project Manager
LIST OF APPENDICES
Appendix 1 Figure No. 1—Site Vicinity Map
Figure No. 2— ESHWT Boring Location Plan
Appendix 2 Boring Logs
3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com

Summary of ESHWT Determinations SUMMIT Project No. 0109.G0046
Underwood Road November 23, 2022
SUMMIT
ENGINEERING • LABORATORY • TESTING
A Universal Engineering Sciences Company
APPENDIX 1
Figures
3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com

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Figure 1 Weddington Road
Site Location Plan Wesley Chapel, North Carolina SUMMIT
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ESHWT Boring Location Plan Weddington Road SUMMIT
Approx. Soil Test Boring Location Wesley Chapel, North Carolinar.a...
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3575 Centre Circle
SUMMIT Project No.: 0109.G0046 Fort Mill,South
171Carolina 29715
SCALE: NTS (803)s04o4-1717

Summary of ESHWT Determinations SUMMIT Project No. 0109.G0046
Underwood Road November 23, 2022
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SUMMIT
ENGINEERING • LABORATORY • TESTING
A Universal Engineering Sciences Company
APPENDIX 2
Boring Logs
3575 Centre Circle Drive, Fort Mill, SC 29715 summit-companies.com

SUMMIT ENGINEERING, LABORATORY 8c TESTING,INC. BORING NUMBER SW-16
3575 CENTRE CIRCLE
Milk FORT MILL,SOUTH CAROLINA PAGE 1 OF 1
SUMMIT TELEPHONE: [phone]
►_ �-• SUMMIT-COMPANIES.COM
CLIENT Shea Homes PROJECT NAME Underwood Road
PROJECT NUMBER 0109.G0046 PROJECT LOCATION Wesley Chapel, North Carolina
DATE STARTED 11/10/22 COMPLETED 11/10/22 GROUND ELEVATION HOLE SIZE 6 inches
DRILLING CONTRACTOR SUMMIT GROUND WATER/CAVE-IN:
DRILLING METHOD Hollow Stem Auger AT TIME OF DRILLING ---GW NE ATD/Caved in Depth @ 6'bgs
LOGGED BY D.Smith CHECKED BY N.Sacks AT END OF DRILLING ---GW NE>24 hrs
NOTES See Figure 2"Boring Location Plan"for Approx. Boring Location AFTER DRILLING ---
w o A SPT N VALUE A
0 U o >- ci w 0 20 40 60 80 100
_ �w H�
Q 0 MATERIAL DESCRIPTION J 2 >0 9,n Q
J a O. m O> 0 20 40 60 80 100
(3 2z (.) oz
w < ❑FINES CONTENT(%)❑
0 20 40 60 80 100
—'"• • • Approx.3"of TOPSOIL
(ML)RESIDUUM:
Soft Moist Yellowish Red(5YR,5/8)Sandy SILT
SPT 1-1-2-2 A
1 (3)
•
(ML)Very Soft Moist Strong Brown(7.5YR,4/6)Sandy SILT
2.5
SPT 2-1-1-1
2 (2)
5.o SPT 0-1-1-2
3 (2)
•
(SM)Partially Weathered Rock When Sampled Becomes Light'it -
Brownish Gray(2.5Y,6/2)Silty SAND with Rock Fragments SPT 15-50
1 4 (50/4")
7.5
SPT 50 >>A
Bottom of Boring at 8.2 feet bgs,Auger Refusal 5 (50/2")
io.o

SUMMIT ENGINEERING, LABORATORY 8c TESTING,INC. BORING NUMBER SW-17
3575 CENTRE CIRCLE
— FORT MILL,SOUTH CAROLINA PAGE 1 OF 1
SUMMIT TELEPHONE: [phone]
-►_ ---—. SUMMIT-COMPANIES.COM
CLIENT Shea Homes PROJECT NAME Underwood Road
PROJECT NUMBER 0109.G0046 PROJECT LOCATION Wesley Chapel, North Carolina
DATE STARTED 11/14/22 COMPLETED 11/14/22 GROUND ELEVATION HOLE SIZE 6 inches
DRILLING CONTRACTOR SUMMIT GROUND WATER/CAVE-IN:
DRILLING METHOD Hollow Stem Auger AT TIME OF DRILLING ---GW NE ATD/Caved in Depth @ 9.5'bgs
LOGGED BY D.Smith CHECKED BY N.Sacks AT END OF DRILLING ---GW NE>24 hrs
NOTES See Figure 2"Boring Location Plan"for Approx. Boring Location AFTER DRILLING ---
w o A SPT N VALUE A
0 U >-ct >- cow 0 20 40 60 80 100
_ I—w EC^ Hn
It
Q ,..,1-
O MATERIAL DESCRIPTION J 2 >0 9O n Q 1 M
" J o O. m O> 0 20 40 60 80 100
(3 2z () oz
w < ❑FINES CONTENT(%)❑
co
0 20 40 60 80 100
--'" ``, Approx.3"of TOPSOIL
(MH)RESIDUUM:
Firm Yellowish Red(5YR,5/8)Sandy Elastic SILT SPT 3-3-5-6
1 (8)
(MH)Very Stiff Yellowish Red(5YR,5/8)and Yellow(10YR,7/8)
2.5 Sandy Elastic SILT with Rock Fragments
SPT 6-9-9-8
2 (18)
(MH)Very Stiff Yellowish Red(5YR,5/8)and Yellow(10YR,7/8)
Sandy Elastic SILT
5.0 SPT 5-8-8-8
3 (16)
(ML)Very Stiff Brownish Yellow(10YR,6/8),Light Red(2.5YR,
6/8),and Light Gray(2.5Y,7/1)Slightly Clayey Sandy SILT
SPT 6-7-11-20
4 (18)
7.5
(ML)Hard Brown(10YR,5/3)and Light Gray(2.5Y, 7/1)Slightly
Clayey Sandy SILT with Manganese Stains
SPT 8-18-18-19
5 (36)
9.5ft 11
10.0
(ML)Hard Brown(10YR,5/3)and Light Gray(2.5Y, 7/1)Sandy
SILT with Clay Seams and Manganese Stains
SPT 6-23-27-50
6 (50) '••• ••
': (ML)Partially Weathered Rock When Sampled Becomes Brown SPT 38-50
z.s ,', (10YR,5/3)and Light Gray(2.5Y,7/1)Sandy SILT with Rock 7 (50/1")
\ Fragments and Manganese Stains
Bottom of Boring at 12.6 feet bgs,Auger Refusal
15.0