SW5220302_Soils/Geotechnical Report (SHWT)_20220406

SEASONAL HIGH WATER TABLE DETERMINATION
North Carolina National Guard JFHQ Helipad Site
District Drive
Raleigh, NC 27607
Timmons Group Project No.: 42866
Prepared for:
Rodney D. Newton, LTC
1636 Gold Star Drive, Suite 2600 (CFMO)
Raleigh, NC 27607
Prepared By:
f
TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
5410 Trinity Rd., Ste 102
Raleigh, NC 27607
Phone: [phone]
Fax: [phone]
www.timmons.com
February 20, 2020
Robin Maycock Perez, LSS

EXECUTIVE SUMMARY
On behalf of North Carolina National Guard, Timmons Group Senior Environmental
Project Manager and Licensed Soil Scientist, Robin M. Perez, conducted a soil investigation on
December 18, 2019 to identify the Seasonal High Water Table (SHWT) within the proposed
stormwater control measure (SCM) location and within the NC National Guard JFHQ Helipad
Site project limits (hereafter referred to as "Site").
The Site encompasses approximately 14.01 acres and is located in Raleigh, NC within
Wake County (See Figure 1. Vicinity Map). The Site is bound by District Road to the north, and
by Wade Avenue to the south. To the east, the Site is bound by commercial development and to
the west, by forested uplands and commercial development. The Site is located within the
Piedmont physiographic province and within the Neuse River Basin (HUC 03020201803),
within the Middle Creek- Neuse sub watershed and drains towards Richlands Creek. Site
topography includes steep slopes above a small stream valley, due to fill material. There is one
stream feature on the Site and no wetlands were identified by Timmons in January 2019.
SHWT at the Site was determined by hand auger. Soil boring 1 was advanced to a depth
of 102 inches below the ground surface (bgs). Chroma 2 redoximorphic features indicative of
SHWT were not observed in the boring. Auger refusal was experienced at 102 inches below the
soil surface at borehole 1 due to rock. Soil Boring 2 was advanced to 28 inches bgs in the stream
floodplain in order to extrapolate the SHWT in the vicinity of the proposed SCM. Table 1 below
shows the observed depth to auger refusal and SHWT below the existing soil surface.
Table 1: Soil Observation Summary
Boring
ID
Auger Refusal'
in
SHWT Depth'
(in)
SHWT Elevation
(approximate)
1
102
102+
420
2
NA
24
420
'Depth below existing soil surface
The area investigated by auger boring 1 consisted of layers of fill, with no indication of seasonal
high-water table above 102 inches depth bgs. However, infiltration rates may be compromised
due to the nature of the fill, which consisted of concrete millings and some compacted layers and
subsoil. The soil boring was located where the landscape position was convex, above a steep
side slope and approximately 6 feet above the adjacent stream valley bottom, where soil boring 2
identified SHWT at approximately 24 — 28 inches bgs. Roughly extrapolating the SHWT from
the valley bottom suggests that the SHWT could be at approximately 8 — 8.5 feet bgs. This
could not be confirmed at the soil boring 1 location due to auger refusal due to rock. The rock
encountered may or may not be bedrock and could be just a rock larger than the auger bucket
diameter (3").
SHWT Determination
NC NG JFHQ Helipad
Page i
Timmons Group
December 2019

INTRODUCTION
The Site encompasses approximately 14.01 acres and is located in Raleigh, NC within
Wake County (See Figure 1. Vicinity Map). The Site is bound by District Road to the north, and
by Wade Avenue to the south. To the east, the Site is bound by commercial development and to
the west, by forested upland and commercial development. The Site is located within the
Piedmont physiographic province and within the Neuse River Basin (HUC 03020201803),
within the Middle Creek- Neuse sub watershed and drains towards Richlands Creek.
Site topography includes moderate to steep slopes (2 — 25%) above a small stream valley, with
fill material observed in the area of soil boring 1. There is one stream feature on the Site and no
wetlands were identified by Timmons in January 2019.
SHWT at the Site was determined by hand auger. Soil boring 1 was located within the proposed
Stormwater Control Measure (See Figure 2). Soil Boring 2 was located outside of the SCM area
but was used to observe the SHWT location nearby.
The auger boring was advanced to a depth of 102 inches below the ground surface. Chroma 2
redoximorphic features indicative of SHWT were not observed in the boring. Auger refusal was
experienced at 102 inches below the soil surface at borehole 1 due to rock. Table 1 below shows
the observed depth to auger refusal below the existing soil surface.
METHODOLOGY
Soil Profiles within and nearby to the proposed SCM area were reviewed by advancing a hand
auger to a depth below ground surface of 102 inches, when the auger was stopped by an
individual rock or bedrock. General soil morphological conditions were observed and described
by a licensed soil scientist using standard techniques outlined in the "Field Book for Describing
and Sampling Soils, Version 3" published by the Natural Resources Conservation Service
(NRCS 2012).
The area investigated by auger boring 1 consisted of layers of fill, with no indication of seasonal
high-water table above 102 inches depth below ground surface. However, infiltration rates may
be compromised due to the nature of the fill, which consisted of concrete millings and some
compacted layers. The soil boring was located where the landscape position was convex, above
a steep side slope and approximately 6 feet above the adjacent stream valley bottom. Soil boring
2 was taken in the stream floodplain, where seasonal high-water table was observed at
approximately 24 — 28 inches below the ground surface. Roughly extrapolating the SHWT
from the valley bottom suggests that the SHWT could be at approximately 8 — 8.5 feet below
ground surface. This could not be confirmed at soil boring 1 due to auger refusal due to rock at
8.5 feet or 102 inches below ground surface. The rock encountered may or may not be bedrock
and could be just a rock larger than the auger bucket diameter (3").
SHWT Determination Package Timmons Group
PROJECT NAME MONTH YYYY
Page 1

SITE GEOLOGY AND HYDROGEOLOGY
The Site is mapped as primarily Cecil and Pacolet soil series, which are deep, well drained
upland soils found on ridges and side slopes in the central part of Wake County. These soils are
underlain by metamorphic gneiss and schist, described as the Raleigh Belt, which is mapped as
predominantly metamorphic felsic and biotite gneiss and schist.
SOIL BORING DESCRIPTIONS
SOIL BORING 1
Horizon
Depth
Munsell color
Texture
Structure
AX
0-6
10 YR 4/3
loam
friable
AX
6 - 12
7.5YR 6/4
Silt loam
wksbk
A/U
12 — 15
7.5YR 8/1
loam
Loose, wksbk
AX
15 - 20
7.5YR4/4
Silty clay loam
msbk
A/U
20 — 32
10YR3/1
Loam/millings
massive
B
32- 42
2.5YR4/6
Clay loam
wksbk
B
42 — 58
2.5YR4/6
clay
massive
BC
58 — 72
5YR5/6
Clay loam
massive
BC
72 — 80
5YR4/6
Clay loam
massive
BC
80 -102
5YR4/6
Clay loam
massive
SOIL BORING 2
Horizon
Depth
Munsell color
Texture
Structure
A
0-2
10YR 4/3
Loam
friable
AB
2 — 24
5YR5/6
Clay loam
wksbk
B
24 — 28
10YR5/4,7/6, 8/1
Clay
wksbk
B
28 — 32
10YR7/6,8.5/N
Clay
wksbk
A/U = Urban fill Wksbk = weak sub angular blocky Msbk = moderately subangular blocky
Soil Boring 1 included layers of fill over subsoil from approximately 12 — 32 inches bgs. The fill
and subsoil below 32 inches bgs were somewhat compacted and massive in structure which
could restrict hydraulic conductivity or infiltration rates. Soil Boring 2 was taken outside of the
SCM area in order to corroborate the SHWT for the general area. SHWT could be estimated to
be at approximately 8.5 feet bgs based on the relative elevations from the two soil borings.
CONCLUSIONS
• The proposed SCM is located on a ridge and side slope at least 6 feet above the small
floodplain nearby.
• The SHWT identified on the Site is at least 8 feet below the ground surface in the area of
the proposed stormwater control measure.
• Depending on the installation depth of the SCM, and if the required 2-foot separation to
SHWT is maintained, no impact to groundwater is anticipated.
Seasonal High Water Table Determination Package Timmons Group
PROJECT NAME MONTH YYYY

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FIGURE 1: VICINITY MAP YOUR VISION ACHIEVED THROUGH OURS.
TIMMONS GROUP JOB NUMBER:42866 U.S.G.S. QUADRANGLE(S): RALEIGH WEST
PROJECT STUDY LIMITS: 14.01 ACRES DATE(S): 2016
LATITUDE: 35.805763 WATERSHED(S): UPPER NEUSE (NEUSE RIVER BASIN)
LONGITUDE:-78.713165 HYDROLOGIC UNIT CODE(S): 03020201
ese D ans and associate ocunnents are t e exc usrve Drooertv o and may not ce repro uce In w o e Orin Dart an s a no a use or anv Duroose w a[soever. Inc usrve. ut not
construction, bidding, and/or construction staking without the express written consent of TI MMONS GROUP.

PROPOSED PROPERTY LINE
APPROVED DISPOSAL OF
SURPLUS RIGHT OF WAY
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TEST PIT BORING DATA
T-1: 9 FEET OF UNSTRUCTURED FILL
T-2: 8.5 FEET OF UNSTRUCTURED FILL
T-3: 6 FEET OF UNSTRUCTURED FILL
T-4: 6 FEET OF UNSTRUCTURED FILL
T-5: 6.5 FEET OF UNSTRUCTURED FILL
T-6: 9 FEET OF UNSTRUCTURED FILL
T-7: 8 FEET OF UNSTRUCTURED FILL
T-8: NO FILL (NATIVE SOILS)
T-9: NO FILL (NATIVE SOILS)
NOTES
1.
TEST PIT BORING DATA
T-1: 9 FEET OF UNSTRUCTURED FILL
T-2: 8.5 FEET OF UNSTRUCTURED FILL
T-3: 6 FEET OF UNSTRUCTURED FILL
T-4: 6 FEET OF UNSTRUCTURED FILL
T-5: 6.5 FEET OF UNSTRUCTURED FILL
T-6: 9 FEET OF UNSTRUCTURED FILL
T-7: 8 FEET OF UNSTRUCTURED FILL
T-8: NO FILL (NATIVE SOILS)
T-9: NO FILL (NATIVE SOILS)
NOTES
1.
ALL CONSTRUCTION SHALL COMPLY WITH ALL APPLICABLE
8.
NCSCO AND OSHA STANDARDS.
2.
THE CONTRACTOR SHALL RECYCLE ALL PAVING MATERIALS
REMOVED FROM THE SITE AND SHALL PROVIDE
9.
DOCUMENTATION (SWARWEB) THAT THE MATERIALS HAVE
10.
BEEN RECYCLED.
3.
DISPOSE OFF -SITE WASTE MATERIALS GENERATED DURING
11.
CONSTRUCTION AND FOR OBTAINING ALL APPLICABLE
PERMITS FOR OFF -SITE STOCKPILES AND/OR WASTE AREAS.
IF THE SAME PERSON CONDUCTS THE LAND -DISTURBING
ACTIVITY AND ANY RELATED BORROW OR WASTE ACTIVITY,
12.
THE RELATED BORROW OR WASTE ACTIVITY IS PART OF THE
13.
LAND DISTURBING ACTIVITY. IF THE BORROW OR WASTE
ACTIVITY ARE NOT CONDUCTED BY THE SAME PERSON, THEY
SHALL BE CONSIDERED SEPARATE LAND DISTURBING
ACTIVITY AND MUST BE PERMITTED THROUGH THE SEDIMENT
14.
POLLUTION CONTROL ACT.
4.
REPAIR OR REPLACE ANY ITEMS DAMAGED DUE TO
CONSTRUCTION (ONSITE AND/OR OFFSITE) AT NO EXPENSE
13.
TO THE OWNER.
S.
COORDINATE THE PROJECT SCHEDULE WITH THE OWNER,
OWNER'S CIVIL ENGINEER, AND OWNER'S MATERIAL TESTING
5.
AGENT. COORDINATE THE PROJECT SCHEDULE WITH ALL
PARTIES IN ACCORDANCE WITH THE OWNER'S ONGOING
ONSITE OPERATIONS.
6. ALL STORM DRAINAGE PIPES AND STRUCTURES SHALL BE
THOROUGHLY FLUSHED OF ALL SEDIMENT FOLLOWING SITE
STABILIZATION. INTERIOR FLUSHING OF SYSTEM SHALL BE
PERFORMED AS NEEDED TO MAINTAIN PROPER FUNCTIONING
OF THE DRAINAGE SYSTEM.
7. MAINTAIN ALL EROSION CONTROL DEVICES AFTER EACH
RAINFALL EVENT IN ACCORDANCE WITH NCDEQ LAND
QUALITY REQUIREMENTS AND AS DIRECTED BY THE CIVIL
ENGINEER.
1 j fl I fl � fl
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IN DISTURBED AREAS, AMEND THE TOP 6 INCHES OF LAWN
AREAS WITH 3 INCHES OF IMPORTED AND TESTED TOPSOIL
THAT MEET THE SPECIFICATIONS.
ALL SIDEWALKS SHALL HAVE MAX CROSS SLOPE OF 2%.
ALL ADA PARKING SPACES SHALL NOT EXCEED 2% SLOPE IN
ANY DIRECTION.
INSTALL ALL STORM SEWERS TO PROVIDE REQUIRED
CLEARANCES TO CROSSING UTILITIES AS INDICATED IN THE
DRAWINGS AND SPECIFICATIONS.
PROVIDE AN AS -BUILT SURVEY OF ALL UTILITY AND STORM
PHASE DEMOLITION AND NEW CONSTRUCTION TO ENSURE
UNINTERRUPTED ACCESS AND TO ADJACENT FACILITIES.
COORDINATE SHORT-TERM, OFF -HOUR, TEMPORARY SHUT-
DOWNS WITH THE OWNER.
SEE GENERAL NOTES ON EXISTING CONDITIONS AND
DEMOLITION PLAN FOR REQUIREMENTS FOR REMOVAL AND
PATCHING OF PAVEMENT FOR UTILITY INSTALLATION.
ALL ROOF DRAINS SHALL BE 6" PVC (SCH 40) @ 1.04% MIN.
SLOPE UNLESS INDICATED OTHERWISE. USE DUCTILE IRON
WHEN COVER IS LESS THAN 24-IN.
REFER TO PROJECT SPECIFICATIONS FOR ADDITIONAL
INFORMATION.
KEY NOTES
tC5.3TRENCH DRAIN
FLARED END SECTION
DRAINAGE MANHOLE
C5.3
STORM SEWER TRENCHES
C5.3
STANDARD CONCRETE DROP INLET
C5.3
STANDARD CATCH BASIN
C5.3
FOR REVIEW ONLY
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