20010210 Summary Letter for ESHWT Ayrsley - BMP

September 11, 2019

Mr. Matt Murphy
Alliance Realty Partners, LLC
200 Providence Road, Suite 250
Charlotte, North Carolina 28207, North Carolina 28262
Email: [e-mail]

Subject: Estimated Seasonal High Water Table (ESHWT) Determinations
Ayrsley BMP
Pioneer Avenue
Charlotte, North Carolina
SUMMIT Project No. 4951.501

Dear Mr. Davis:

SUMMIT Engineering, Laboratory and Testing, P. C. (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. This report contains a brief description of the project
information provided to us, general site and subsurface conditions revealed during this study.
PURPOSE OF STUDY
The primary purpose of this study was to obtain information regarding the subsurface conditions
near the proposed detention pond, assess the engineering characteristics of the subsurface
materials, and determination of the estimated seasonal high water table mark (if evident). This
report contains the following items:
Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019

2

• Photographic Logs, 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 September 5, 2019 and performed two (2) soil test borings (identified
as Borings BMP-1 and BMP-2) in the proposed detention pond. We also performed one (1) offset
boring (identified as Boring BMP-1A) due to shallow auger refusal encountered in Boring BMP-
1. The approximate locations of the borings are shown on Figure 2 – “Boring Location Plan”
provided in Appendix 2. The client (Alliance Realty Partners, LLC) provided SUMMIT a plan
that indicated the approximate location of the proposed detention pond and test locations. 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
boring locations be surveyed to determine existing ground elevation and the actual test locations.
The soil test borings were performed using an ATV-mounted CME 550X drill rig, and extended
to approximate depths of ranging from 2.6 to 12 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 at designated
intervals 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 each 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
Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019

3

symbols are depicted on the “Boring Log” provided in Appendix 3.
GENERALIZED SUBSURFACE STRATIGRAPHY
General subsurface conditions observed during our geotechnical study are described herein. For
more detailed soil descriptions and stratifications at a particular test location, the respective
“Boring Log” provided in Appendix 3 should be reviewed. The horizontal stratification lines
designating the interface between various strata represent approximate boundaries. Transitions
between different strata in the field may be gradual in both the horizontal and vertical directions.
Beginning from the ground surface, residual (undisturbed) soils were encountered that consisted
of silty sands. Partially weathered rock (PWR) conditions were encountered in Borings BMP-1
and BMP-2 beginning at approximate depths of 2 and 4 feet below the existing ground surface,
respectively. Auger refusal conditions were encountered in Borings BMP-1, BMP-1A and BMP-
2 at approximate depths of 2.6, 3 and 12 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
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
Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019

4

ground water 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, Estimated Seasonal High Water Table (ESHWT) indicators (water
stained soils) indicators were not evident in soils sampled in the borings. However, even though
groundwater and ESHWT indicators were not observed in the borings, perch water conditions can
develop above the 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 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
Test
Location
Boring
Depth
(Feet)1
ESHWT
Depth
(Feet) 1
GW
Depth
ATD
(Feet) 1
GW
Depth
After
24 Hours
(Feet) 1
Partially
Weathered
Rock
Approx.
Depth,
(Feet)1
Auger
Refusal
Approx.
Depth,
(Feet)1
BMP-1 2.6 NE NE NE 2 2.6
BMP-1A 3 NE NE NE N/A 3
BMP-2 12 NE NE NE 4 to 9 and 10 12
1 Depths from existing ground surface. N/A – Not applicable for auger probe borings
NE – Not Encountered in Boring.
Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019
5
The analyses and recommendations submitted in this report were based, in part, on data obtained
from this study. 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.
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
Todd A. Costner, E.I. Kerry C. Cooper, PE
Senior Professional Geotechnical Department Manager
LIST OF APPENDICES
1 Photographic Log
2 Figure No. 1 – Site Location Map
Figure No. 2 – Test Location Plan
3 Summary of Tet Pit Observation Sheet
9/11/19
Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019

6

APPENDIX 1
Photographic Log

Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019

7

Boring BMP-1
(Approximate Depth = 0 to 2.6 feet below existing ground surface)

Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019

8

Boring BMP-2
(Approximate Depth = 0 to 10 feet below existing ground surface)

Boring BMP-2
(Approximate Depth = 10 to 12 feet below existing ground surface)
Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019

9

APPENDIX 2
Figures
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Figure 1
Site Vicinity Map
Ayrsley BMP
Pioneer Avenue
Charlotte, Nort Carolina
CELEBRATING 15 YEARS
SUMMIT
SCALE: NTS
SUMMIT Project No.: 4951.501
ENGINEERING, LABORATORY & TESTING, P.C.
3575 Centre Circle
Fort Mill, South Carolina 29715
[phone]

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Boring locations were not
surveyed and should be
considered approximate
Figure 2
Boring Location Plan
Approx. Test Pit Location
BMP-2 N _
ESHWT - NE '''�
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j(r_`�� �`� \�h\
: MP-lA .._ � � \ \ �"\
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Ayrsley BMP
Pioneer Avenue
Charlotte, Nort Carolina
SUMMIT
SCALE: NTS
SUMMIT Project No.: 4951.501
3575 Centre Circle
Fort Mill, South Carolina 29715
[phone]

Summary of ESHWT Determination SUMMIT Project No. 4951.501
Ayrsley BMP September 11, 2019

9

APPENDIX 3
Boring Logs

PROJECT NUMBER 4951.501 PROJECT LOCATION Charlotte, Mecklenburg County, North Carolina
PROJECT NAME Ayrsley BMPCLIENTAlliance Realty Partners, LLC
ABBREVIATIONS
TV
PID
UC
ppm
-
-
-
-
TORVANE
PHOTOIONIZATION DETECTOR
UNCONFINED COMPRESSION
PARTS PER MILLION
LIQUID LIMIT (%)
PLASTIC INDEX (%)
MOISTURE CONTENT (%)
DRY DENSITY (PCF)
NON PLASTIC
PERCENT PASSING NO. 200 SIEVE
POCKET PENETROMETER (TSF)
LL
PI
W
DD
NP
-200
PP
-
-
-
-
-
-
-
Standard Penetration Test
SAMPLER SYMBOLSLITHOLOGIC SYMBOLS
(Unified Soil Classification System)
WELL CONSTRUCTION SYMBOLS
KEY TO SYMBOLS
Water Level at Time
Drilling, or as Shown
Water Level After 24
Hours, or as Shown
Water Level at End of
Drilling, or as Shown
AUGER: Auger Probe
BLANK
SM: USCS Silty Sand
PWR: Partially Weathered Rock
SUMMIT Engineering, Laboratory & Testing, P.C.
3575 Centre Circle
Fort Mill, South Carolina 29715
704.504.1717
summit-companies.com
SPT
1
SPT
2
(SM) RESIDUUM:
Dense Light Olive Brown (2.5Y, 5/6), White (White, 2.5YR, 9.5/1)
and Black (2.5Y, 2.5/1) Micaceous Silty Fine to Medium SAND
(SM) Partially Weathered Rock (PWR) when sampled becomes
Strong Brown (7.5YR, 5/8), White (White, 2.5YR, 9.5/1) and
Black (7.5YR, 2.5/1) Micaecous Silty SAND
Bottom of Boring at 2.6 feet bgs, Auger Refusal
4-21-22-26
(43)
33-50
(50/1")
NOTES See Figure 2 "Boring Location Plan" for Approx. Boring Location
GROUND ELEVATION
LOGGED BY D. Robles
DRILLING METHOD Hollow Stem Auger
DRILLING CONTRACTOR SUMMIT
CHECKED BY
DATE STARTED 9/5/19 COMPLETED
AT TIME OF DRILLING --- GW NE ATD
AT END OF DRILLING --- GW NE > 24 Hrs
HOLE SIZE 6 inches
GROUND WATER/CAVE-IN:
AFTER DRILLING ---
RE
C
O
V
E
R
Y

%
(R
Q
D
)
20 40 60 800 100
PL LLMC
FINES CONTENT (%)
20 40 60 800 100
GR
A
P
H
I
C
LO
G
EL
E
V
A
T
I
O
N
(f
t
.
)
2.5
5.0
7.5
10.0
12.5
15.0
SA
M
P
L
E

T
Y
P
E
NU
M
B
E
R
MATERIAL DESCRIPTION
BL
O
W
CO
U
N
T
S
(N

V
A
L
U
E
)
SPT N VALUE
20 40 60 800 100
PAGE 1 OF 1
BORING NUMBER BMP-1
PROJECT NUMBER 4951.501 PROJECT LOCATION Charlotte, Mecklenburg County, North Carolina
PROJECT NAME Ayrsley BMPCLIENTAlliance Realty Partners, LLC
SUMMIT Engineering, Laboratory & Testing, P.C.
3575 Centre Circle
Fort Mill, South Carolina 29715
704.504.1717
summit-companies.com
>>
Auger Probed to an approx. depth of 3 feet bgs
Bottom of Boring at 3 feet bgs, Auger Refusal
NOTES Boring Offset Approx. 5' North of BMP-1
GROUND ELEVATION
LOGGED BY D. Robles
DRILLING METHOD Hollow Stem Auger
DRILLING CONTRACTOR SUMMIT
CHECKED BY
DATE STARTED 9/5/19 COMPLETED
AT TIME OF DRILLING --- GW NE ATD
AT END OF DRILLING --- GW NE > 24 Hrs
HOLE SIZE 6 inches
GROUND WATER/CAVE-IN:
AFTER DRILLING ---
RE
C
O
V
E
R
Y

%
(R
Q
D
)
20 40 60 800 100
PL LLMC
FINES CONTENT (%)
20 40 60 800 100
GR
A
P
H
I
C
LO
G
EL
E
V
A
T
I
O
N
(f
t
.
)
2.5
5.0
7.5
10.0
12.5
15.0
SA
M
P
L
E

T
Y
P
E
NU
M
B
E
R
MATERIAL DESCRIPTION
BL
O
W
CO
U
N
T
S
(N

V
A
L
U
E
)
SPT N VALUE
20 40 60 800 100
PAGE 1 OF 1
BORING NUMBER BMP-1A
PROJECT NUMBER 4951.501 PROJECT LOCATION Charlotte, Mecklenburg County, North Carolina
PROJECT NAME Ayrsley BMPCLIENTAlliance Realty Partners, LLC
SUMMIT Engineering, Laboratory & Testing, P.C.
3575 Centre Circle
Fort Mill, South Carolina 29715
704.504.1717
summit-companies.com
SPT
1
SPT
2
SPT
3
SPT
4
SPT
5
SPT
6
SPT
7
(SM) RESIDUUM:
Loose Light Yellowish Brown (2.5Y, 6/4) and White (2.5Y, 8/1)
Micaceous Silty SAND
(SM) Medium Dense Pale Brown (2.5Y, 8/3) and White (2.5Y,
8/1) Slightly Micaceous Silty SAND
(SM) Partially Weathered Rock (PWR) when sampled becomes
Pale Brown (2.5Y, 8/3) and White (2.5Y, 8/1) Slightly Micaceous
Silty SAND
(SM) Dense Very Pale Brown (10YR, 7/3), White (2.5YR, 9.5/1)
and Black (10YR, 2.5/1) Slightly Micaecous Silty SAND
(SM) Partially Weathered Rock (PWR) When Sampled Becomes
Very Pale Brown (10YR, 7/3) Slightly Micaecous Silty SAND
Bottom of Boring at 12 feet bgs, Auger Refusal
3-4-4-5
(8)
8-16-29-50/4"
(24)
24-24-50
(50/3")
50
(50/3")
15-16-19-21
(35)
11-50
(50/5")
50
(50/0")
NOTES See Figure 2 "Boring Location Plan" for Approx. Boring Location
GROUND ELEVATION
LOGGED BY D. Robles
DRILLING METHOD Hollow Stem Auger
DRILLING CONTRACTOR SUMMIT
CHECKED BY
DATE STARTED 9/5/19 COMPLETED
AT TIME OF DRILLING --- GW NE ATD
AT END OF DRILLING --- GW NE > 24 Hrs
HOLE SIZE 6 inches
GROUND WATER/CAVE-IN:
AFTER DRILLING ---
RE
C
O
V
E
R
Y

%
(R
Q
D
)
20 40 60 800 100
PL LLMC
FINES CONTENT (%)
20 40 60 800 100
GR
A
P
H
I
C
LO
G
EL
E
V
A
T
I
O
N
(f
t
.
)
2.5
5.0
7.5
10.0
12.5
15.0
SA
M
P
L
E

T
Y
P
E
NU
M
B
E
R
MATERIAL DESCRIPTION
BL
O
W
CO
U
N
T
S
(N

V
A
L
U
E
)
SPT N VALUE
20 40 60 800 100
PAGE 1 OF 1
BORING NUMBER BMP-2
PROJECT NUMBER 4951.501 PROJECT LOCATION Charlotte, Mecklenburg County, North Carolina
PROJECT NAME Ayrsley BMPCLIENTAlliance Realty Partners, LLC
SUMMIT Engineering, Laboratory & Testing, P.C.
3575 Centre Circle
Fort Mill, South Carolina 29715
704.504.1717
summit-companies.com
>>
>>
>>
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