SW3230302_Soils/Geotechnical Report_20240417 (2)

March 4, 2024 /Zak
Ms. Rebecca Monteith
MI Homes SUMMIT
5350 77 Center Drive, Suite 100 ENGINEERING •LABORATORY•TESTING
Charlotte, NC 28217 A 9 VES COMPANY
Email: [e-mail] :.
Subject: Estimated Seasonal High Water Table (ESHWT) Determinations
Davis Village ESHWT
Phifer Road
Wingate, North Carolina
SUMMIT Project No. A24117.00423.000
Dear Ms. Monteith:
SUMMIT Engineering, Laboratory and Testing, Inc. (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) determinations in the proposed stormwater BMP pond 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 pond, assess the engineering characteristics of the
subsurface materials, and determination of the estimated seasonal high water table mark (if
evident).
10121 Pineville Distribution St., Pineville, NC 28134 summit-companics.com

Summary of ESHWT Determinations SUMMIT Project No.A24117.00423.000
Davis Village ESHWT March 4, 2024
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 February 2 of 2024 and performed one (1) soil test boring (identified
as SW-1) in the proposed stormwater BMP pond. The approximate location of the boring is
shown on Figure 2 — "ESHWT Boring Location Plan" provided in Appendix 2. The client (MI
Homes) provided SUMMIT a plan sheet titled "Davis Village" prepared by Plott Hound
Engineering dated May 1, 2022, that indicated the approximate location of the proposed
stormwater BMP pond. The boring was located by professionals from our office using the
provided plan, recreation-grade handheld GPS, existing topography, and aerial maps as
reference. Since the boring location was not surveyed, the location of the boring should be
considered approximate. We recommend the actual boring location be surveyed to determine
the actual boring location and existing ground elevation.
The soil test boring was performed using a track mounted TMG CSR-174. The boring was
extended to an approximate depth of fourteen and nine tenths (14.9) 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
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Summary of ESHWT Determinations SUMMIT Project No.A24117.00423.000
Davis Village ESHWT March 4,2024
Log" 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 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 3 inches. Beneath the topsoil layer, residual (undisturbed) soils were
encountered that consisted of sandy silts (ML). Partially Weathered Rock (PWR) materials were
encountered in Boring SW-1 at approximate depths of 1 and 14.4 feet below the existing ground
surface.
GROUNDWATER LEVEL MEASUREMENTS
At the time of drilling, groundwater was not observed in the boring. After waiting more than 24
hours, groundwater was not observed in the boring. 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
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
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Summary of ESHWT Determinations SUMMIT Project No.A24117.00423.000
Davis Village ESHWT March 4, 2024
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 evident in soils sampled in Boring SW-1.
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 Approx. Refusal
Test Depth Depth ATD 24 Hours Depth Surface Depth
Location (Feet)" (Feet) (Feet)' (Feet)' (Feet)' (Feet) (Feet)"
SW-1 14.9 13.5 NE NE 14.4 557.88 NE
1 Depths from existing ground surface.
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.
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Summary of ESHWT Determinations SUMMIT Project No.A24117.00423.000
Davis Village ESHWT March 4, 2024
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.
bAkci.z)&- Ca441Z1 /(L--
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 Log
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Summary of ESHWT Determinations SUMMIT Project No.A24117.00423.000
Davis Village ESHWT March 4, 2024
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SUMMIT
ENGINEERING • LABORATORY • TESTING
A U E S COMPANY
APPENDIX 1
Figures
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10121 Pineville Distribution St., Pineville, NC 28134 summit-companics.com

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Summary of ESHWT Determinations SUMMIT Project No.A24117.00423.000
Davis Village ESHWT March 4,2024
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SUMMIT
ENGINEERING • LABORATORY • TESTING
A IVO U E S IM CC)MPANY
APPENDIX 2
Boring Log
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10121 Pineville Distribution St., Pineville, NC 28134 summit-companics.com

SUMMIT ENGINEERING,LABORATORY,&TESTING,INC. BORING NUMBER SW-1
3575 CENTRE CIRCLE PAGE 1 OF 1 FORT MILL/SOUTH CAROLINA 2971 5
SUMMIT 704-504-1717
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CLIENT MI Homes PROJECT NAME Davis Village ESHWT
PROJECT NUMBER A24117.00423.000 PROJECT LOCATION Wingate, North Carolina
DATE STARTED 2/20/24 COMPLETED 2/20/24 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
LOGGED BY J. Flores CHECKED BY Z. Rodriguez 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 11 O MATERIAL DESCRIPTION J 2 >0 9O n Q 1 M
" J a D 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
_ � pP Topsoil
(ML)Fill: Partially Weathered Rock when sampled becomes Pale SPT 8-20-50
— : Brown(10YR,6/3)Sandy SILT 1 (70)
(ML)RESIDUUM:Stiff Pale Brown(10YR,6/3)and Yellow
(10YR,8/8)Sandy SILT
SPT 7-5-6-8
— —. 2 (11)
•
(ML)Very Stiff Pale Brown(10YR,6/3)and Brownish Yellow
s.o • (10YR,6/8 Sandy SILT with Manganese Stains SPT 6-7-11-18
3 (18)
(ML)Hard Yellowish Brown(10YR,5/4)and Pale Brown(2.5,8/2
Sandy SILT with Manganese Stains SPT 10 16 21 21
4 (37)
SPT 8-18-29-35
5 (47)
SPT 9-20-37-49
6 (57)
SPT 8-10-27-38
7 (37)
" • (ML)Partially Weathered Rock when sampled becomes SPT 24-50
Yellowish Brown 10YR,5/4)and Pale Brown(2.5,8/2 Sandyg (50/5")
SILT with Manganese Stains
Bottom of Boring at 14.9 feet bgs. Boring Terminated
20.0