8003_Rowan_MSWLF_PTC_PhaseVDesignHydro_FID1706384_20220826

Rowan County Landfill I Phase V Construction Permit Application
5 — Design Hydrogeological Report
5 — Design Hydrogeological
Report

Rowan County Landfill I Phase V Construction Permit Application ���
5 — Design Hydrogeological Report
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Site Hydrogeologic
Characterization
Report
Rowan County Landfill
Proposed Phase V Expansion
Rowan County North Carobna
August 2022

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Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Contents
Contents
1 General Information...................................................................................................1
1.1 Introduction.............................................................................................................1
1.2 Background............................................................................................................1
1.3 Purpose..................................................................................................................2
2
3
Site Topography and Geographical Setting...............................................................2
2.1
Topographic Setting...............................................................................................2
2.2
Spring, Streams, and Drainage Features................................................................2
2.3
Existing or Abandoned Wells..................................................................................2
2.4
Rock Outcrops (Trends, Strikes, and Dips).............................................................3
2.5
Other Features Affecting Site Suitability.................................................................3
2.6
Groundwater Discharge Features...........................................................................3
2.7
Hydrogeological Properties of Bedrock...................................................................3
Hydrogeologic and Geotechnical Investigation..........................................................4
3.1
Boring Records.......................................................................................................4
3.1.1 Number of Borings......................................................................................4
3.1.2 Location of Borings.....................................................................................5
3.1.3 Sampling.....................................................................................................6
3.1.3.1 Soil Sampling..............................................................................................6
3.1.3.2 Rock Coring................................................................................................6
3.1.4 Boring Logs.................................................................................................6
3.1.5 Piezometers and Monitoring Wells..............................................................6
3.1.6 Soil Characteristics.....................................................................................6
3.1.7 Sealing of Borings.......................................................................................7
3.2
Description of Soil Units..........................................................................................7
3.2.1 Regional Geology.......................................................................................7
3.2.2 Local Geology.............................................................................................8
3.2.3 Fault Areas.................................................................................................9
3.2.4 Seismic Impact Zones...............................................................................10
3.3
Water Table Information.......................................................................................10
3.3.1 Groundwater Level Measurements...........................................................10
3.3.2 Vertical Flow Components........................................................................10
3.3.3 Seasonal and Temporal Factors...............................................................10
3.3.4 Hydraulic Conductivities............................................................................11
3.4
Aquifer Description...............................................................................................11
3.4.1 General.....................................................................................................11
3.4.2 Recharge and Discharge Areas................................................................12
3.4.3 Influence of Natural or Man -Made Actives.................................................12
3.4.4 Maps and Diagrams..................................................................................13

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Contents
4 Water Quality Monitoring Plan.................................................................................13
5 References..............................................................................................................13
Appendices
Appendix A - Maps
Site Vicinity Map
Aerial Map
Appendix B — Hydrogeological Data
Site Plan
Potentiometric Map
Geological Cross Sections
Flownets
Appendix C — Groundwater Data
Groundwater Elevations
Seasonal Water Elevations
Historical Rainfall Totals 1980-Present
Historical Regional Groundwater Level for NC-142
Appendix D — Seismic and Geological Data
Geological Map
Earthquakes in North Carolina Map 1874-2022 (NEIC Earthquake Search Results)
Seismic Impact Zone Map
Appendix E — Boring Logs
Logs of Borings
Piezometer Construction Logs
Appendix F — Soil Laboratory Details
Appendix G — Slug Test Results

Rowan County Landfill i Site Hydrogeologic Charaterization Report ���
General Information
1 General Information - 1 5 NCAC 1 3B.1623(a)(1 )
1.1 Introduction
Rowan County owns and operates a municipal solid waste (MSW) landfill (NCDENR Permit No.
8003) consisting of approximately 375 acres at 789 Campbell Road (SR 1947) in Woodleaf,
North Carolina. Rowan County has operated the landfill since 1989. A closed land clearing and
inert debris (LCID) landfill and a closed construction and demolition (C&D) landfill are located in
the eastern portion of the property.
The primary purpose of this investigation is to provide detailed and localized hydrogeologic
information for engineering design and design of a water quality monitoring system for Phase V
expansion of the existing MSW landfill. The investigation was conducted in general accordance
with North Carolina Department of Environmental Quality, Division of Waste Management -Solid
Waste Section (NCSWS) Rule 15A NCAC 13B .1623 (b) for Design Hydrogeologic Report
assessment.
1.2 Background
In 1989, Rowan County was in the process of closing an unlined landfill and constructing a new
lined Subtitle D landfill. The complete Subtitle D area consists of Phases I — IX with a total
design capacity of approximately 15.071 million cubic yards for MSW. Phases I, II, and III,
totaling 51 acres, have been constructed and began receiving waste in December 1989.
Phase IV, including associated perimeter berms, ditches and haul roads, encompasses
approximately 26 acres, of which about 20 acres is covered with a liner system for waste
placement. The Phase IV area is bounded on the east by a white goods recycling area and
agricultural lands designated for potential future landfill development; on the north by existing
landfill Phase III; on the west by forested land; and on the south by agricultural lands designated
for Phase V landfill development. The Phase V area is currently used as a source for borrow soil
for landfill operations.
Proposed Phase V, including associated perimeter berms, ditches and haul roads,
encompasses approximately 26 acres, of which about 20 acres will be covered with a liner
system for waste placement. The Phase V area is bounded on the east by the existing leachate
aeriation pond and stormwater detention basin for the facility; on the north by existing landfill
Phase IV; on the west by forested land; and on the south by forested and agricultural lands.
A separate MSW landfill development area, consisting of Phases VI - IX, is planned within the
current property boundary east of the active landfill area. Future Phase VI, to the far east of
proposed Phase V, is designated for landfill development and will be used as a source for
borrow soil for landfill operations.

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Site Topography and Geographical Setting
1.3 Purpose
The purpose of the hydrogeologic and geotechnical investigation was to obtain surface and sub-
surface information relevant to the design and operation of the proposed Phase V waste unit.
The investigation area encompasses about 26 acres.
2 Site Topography and Geographical Setting-15A
NCAC 13B.1623(a)(2)
2.1 Topographic Setting- 15A NCAC 13B.1623(a)(2)(A)
The proposed waste management unit is situated on the southern portion of the facility directly
south and adjacent to Phase V. The proposed cell area is actively used as the borrow area for
daily soil cover materials. The primary excavation area is within the eastern portion of the
proposed phase area. The topography is comprised of gently sloping hills and valleys. Within
Phase V, the topography slopes primarily to the south and to the southeast along the eastern
extent. Elevation changes from 702 ft MSL to 658 ft MSL; a change of 44 ft in elevation'.
2.2 Spring, Streams, and Drainage Features .15A NCAC 13B.1623(a)(2)(A)
The area drainage typically flows from higher to lower points of elevation. The surface water
flow ultimately reaches two unnamed tributaries of Second Creek, which flows into the South
Yadkin River. No springs were identified within the immediate vicinity of the proposed Phase V
cell.
2.3 Existing or Abandoned Wells- 15A NCAC 13B.1623(a)(2)(A)
There are no existing or abandoned drinking water wells within the proposed Phase V
expansion of the waste facility boundary. There are a series of monitoring wells installed
throughout the facility and temporary piezometers in the Phase V expansion area. The previous
receptor survey of the landfill property and the adjacent properties, performed by Buxton
Environmental, Inc., 2011, identified several possible water -supply wells within the near vicinity
of the investigation area 2. The only verified water -supply well is identified is Well 35 located at
1217 Old Oak Lane Woodleaf, NC, approximately 880 feet northwest of the proposed waste
expansion area (35°45'5.53"N, 80°33'47.35"W). The impact of the surrounding water -supply
wells to the shallow groundwater aquifer within the Phase V expansion area is assumed to be
negligible due to the proximity of the wells to the proposed expansion and the presumed limited
use/capacity of the residential wells.
' - Source: Rowan County GIS Map Tool; Rowan County GIS Website (rowancountync.gov); 2022 and HDR Aerial
Drone Survey; 2022.
2 - Buxton Environmental, Inc., Design Hydrogeologic Report Revised Proposed Phase IV Subtitle D Municipal Solid
Waste Landfill Expansion Rowan County Landfill, January 2013.

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Site Topography and Geographical Setting
2.4 Rock Outcrops (Trends, Strikes, and Dips) - 15A NCAC
13B.1623(a)(2)(A)
The presence of rock outcrops was not observed within the proposed Phase V waste boundary
or the facility boundary. There are no trends, strikes, or dips that can documented at surface
grade. Borings advanced during this investigation did terminate in bedrock, as further discussed
in Section 3; however, trend, strike, and dip of the underlying bedrock could not be derived from
these boring activities.
2.5 Other Features Affecting Site Suitability -15A NCAC 13B.1623(a)(2)(A)
There are no known or observed additional features that would affect the site suitability for the
proposed Phase V expansion.
2.6 Groundwater Discharge Features -15A NCAC 13B.1623(a)(2)(B)
The Phase V expansion area is bounded by two unnamed tributaries of Second Creek along the
east, west and southern perimeter. These tributaries are natural discharge features for the
shallow unconfined aquifer that will underly the proposed waste unit.
There is an existing French -drain underlying Phases III and IV that runs northwest to southeast
and daylights to the eastern unnamed tributary. This discharge feature directs the groundwater
underneath both Phases to the head waters of the eastern unnamed tributary. The discharge
point is incorporated into the existing WQMP and is monitored semi-annually.
These existing features are not anticipated to impact the constructability, operation, or
monitorability of the proposed Phase V expansion.
2.7 Hydrogeological Properties of Bedrock -15A NCAC 13B.1623(a)(2)(C)
The bedrock underlying the site is an intrusive metamorphosed Gabbro and Diorite from the
Permian Period, based on the 1985 State Geological Map of North Carolina. Rock core samples
collected during installation of well MW-25A indicate that the upper 16 feet of the bedrock is
slightly fractured (RQD = 85-89%) and primarily a coarse -grained Quartz Diorite. Typical
hardness can range from 4 to 7 with a density of 2.8-3 g/cm3. Hydraulic conductivities for
intrusive igneous rock such at diorite range from 10-4 to 10-9 ft/day 3. Since fracturing is very
low, the conductivity is expected to be in the lower range. Characteristics of the bedrock below
this investigation depth of 85 ft bgs are unknown.
3 - Freeze, Allen & Cherry, John, Groundwater, Prentice -Hall, Inc. 1979.

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Hydrogeologic and Geotechnical Investigation
3 Hydrogeologic and Geotechnical Investigation -
15 NCAC 13B.1623(a)(3)through(13)
3.1 Boring Records- 15A NCAC 1313.1623(a)(3)
3.1.1 Number of Borings -15A NCAC 1313.1623(a)(3)
A total of 20 hollow -stem auger (HSA) borings and 36 direct push technology (DPT) borings
were completed within the proposed Phase V cell:
• Eleven borings, PZ5-1 through PZ5-11, were drilled to depths ranging from 18 to 36 feet
below ground surface (bgs) within the interior of the Phase V cell, then converted to
piezometers.
• Nine borings, MW-29 through MW-34A were drilled to depths ranging from 21 to 96 feet
bgs around the perimeter of the Phase V cell, then converted to monitoring wells.
• Thirty-six DPT borings, DPT-1 through DPT-36, were advanced to refusal to evaluate
depth to material that may be difficult to excavate. Note that DPT refusal does not
necessarily correlate to depth to competent bedrock because DPT equipment can be
easily obstructed or impeded by float material such as boulders or quartz lenses.
Table 3-1: HSA Boring Depths and Piezometer/Well Details
Boring ID
Top of
Casing
Elev. (ft)
Depth
(ft bgs)
Screen
Length
(ft)
Screen Interval
(ft bgs)
Well
Diameter
(in)
MW-29A
660.87
83.89
10.00
73.89
- 83.89
2
MW-30
656.15
21.28
10.00
11.28
- 21.28
2
MW-31
670.12
21.32
10.00
11.32
- 21.32
2
MW-32
666.16
22.61
10.00
12.61
- 22.61
2
MW-32A
665.70
96.04
10.00
86.04
96.04
2
MW-33
683.19
30.05
10.00
20.05
- 30.05
2
MW-34
704.75
44.23
10.00
34.23
- 44.23
2
MW-34A
704.61
89.72
10.00
79.72
- 89.72
2
PZ5-1
693.50
35.63
10.00
25.63
- 35.63
2
PZ5-2
679.41
24.57
10.00
14.57
- 24.57
2
PZ5-3
687.94
28.96
10.00
18.96
- 28.96
2
PZ54
689.94
34.61
10.00
24.61
- 34.61
2
PZ5-5
677.31
25.31
10.00
15.31
- 25.31
2
PZ5-6
673.05
20.65
10.00
10.65
- 20.65
2
PZ5-7
669.33
18.10
10.00
8.10
- 18.10
2
PZ5-8
681.73
30.73
10.00
20.73
- 30.73
2
PZ5-9
680.59
29.07
10.00
19.07
- 29.07
2
PZ5-10
677.27
25.29
10.00
15.29
- 25.29
2
PZ5-11
672.81
19.37
10.00
9.37
- 19.37
2
Note: Top of casing elevations surveyed by MLA Design Group, Inc. on February 16, 2022.
4

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Hydrogeologic and Geotechnical Investigation
Table 3-2: DPT Borings Details
Boring ID
Ground
Total Depth
Total Depth
Elev.
(ft bgs)
(ft MSL)*
(ft)*
DPT-1
678
12
666
DPT-2
692
4
688
DPT-3
694
22
672
DPT-4
697
26
671
DPT-5
689
44
645
DPT-6
688
50
638
DPT-7
691
35
656
DPT-8
678
5
673
DPT-9
678
10
668
DPT-10
685
42
643
DPT-11
684
57
627
DPT-12
682
50
632
DPT-13
683
49
634
DPT-14
688
52
636
DPT-15
696
41
655
DPT-16
700
37
663
DPT-17
701
42
659
DPT-18
696
37
659
DPT-19
689
31
658
DPT-20
675
28
647
DPT-21
664
18
646
DPT-22
665
24
641
DPT-23
667
35
632
DPT-24
675
28
647
DPT-25
668
24
644
DPT-26
668
19
649
DPT-27
668
17
651
DPT-28
676
4
672
DPT-29
678
22
656
DPT-30
678
26
652
DPT-31
681
32
649
DPT-32
676
29
647
DPT-33
672
34
638
DPT-34
679
42
637
DPT-35
676
34
642
DPT-36
678
43
635
* - Ground elevations are approximated to the nearest foot based off current topo for the site.
3.1.2 Location of Borings -15A NCAC 13B.1623(a)(3)
Refer to Appendix B for a map showing boring locations relative to the proposed cell locations.
5

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Hydrogeologic and Geotechnical Investigation
3.1.3 Sampling - 15A NCAC 1313.1623(a)(3)&(4)
3.1.3.1 Soil Sampling
Soil sampling was performed in accordance with ASTM D 1586-19, "Standard Test Method for
Penetration Test and Split -Barrel Sampling of Soil". For the majority of borings, samples were
collected using a two -foot split -barrel sampler every five feet from the ground surface to the
planned termination depth. Blow counts were taken at 6-inch intervals to assess the standard
penetration test resistance, or N-value, of the soil. These N-values were used to evaluate the
consistency of the soil.
For the Phase V expansion, standard penetration test intervals varied based on the anticipated
base grade. Appendix E contains the Logs of Borings, which show the sampling intervals for
each boring.
3.1.3.2 Rock Coring
Of the nine HSA borings advanced around the perimeter of the Phase V cell and converted to
monitoring wells, bedrock was only encountered in well MW-29A. Rock coring was performed
from 70 to 85 feet bgs in this boring, in general accordance with ASTM D 2113-14. Each two-
inch core was examined for percent rock core recovery (RCR) and rock quality designation
(RQD), as presented below.
Coring Location Depth (ft bgs) RCR (%) RQD (%)
MW-29A 70-75 100 89 (Good)
75-80 100 86 (Good)
80-85 100 85 (Good)
3.1.4 Boring Logs -15A NCAC 1313.1623(a)(3)
Refer to Appendix E for the boring records.
3.1.5 Piezometers and Monitoring Wells -15A NCAC 1313.1623(a)(3)
Eleven piezometers and nine monitoring wells were constructed over the site as detailed in
Table 3-1 above. Refer to Appendix E for piezometer and monitoring well construction logs.
3.1.6 Soil Characteristics -15A NCAC 13B.1623(a)(4)(E)
The soil onsite exhibited some bedding and had varying particle sizes. The majority of soil
classified as silty SAND (SM) to sandy SILT (ML) with layers of sandy CLAY (CL) to clayey
SAND (SC). The typical permeability for this type of material would range from 1x10-1 to 1x10-3
cm/s (Terzaghi and Peck, 1962).
Undisturbed samples collected from the borings were selected for laboratory testing based on
encountered material types. Constant head permeabilities derived from testing of select material
varied from 1.68 x 10-4 to 6.17 x 10-6 CM/S.

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Hydrogeologic and Geotechnical Investigation
Sample ID
Depth (ft)
Material Type
Lab Permeability Result (cm/s)
MW-29A
9-11
Silty SAND (SM)
1.68 x 10'
MW-31
4-6
Silty Clayey SAND (CL)
2.26 x 10'
PZ5-3
29-31
Silty SAND (SM)
6.32 x 10'
PZ5-5
19-21
Silty SAND (SM)
2.71 x 10-4
PZ5-10
4-6
Sandv SILT (ML)
2.52 x 10-5
3.1.7 Sealing of Borings -15A NCAC 13113.1623(a)(3)
All borings not converted into piezometers were sealed using bentonite slurry that was pumped
through tremie pipe to fill the borehole. Once it is determined exactly which piezometers will
remain for long-term monitoring, the remaining piezometers will be properly abandoned.
3.2 Description of SOII Units- 15A NCAC 13B.1623(a)(1)&(13)
3.2.1 Regional Geology - 15A NCAC 13B.1623(a)(1)&(4)(D)&(13)
The facility is geologically located within the Charlotte Belt of the Piedmont Physiographic
Province of NC 4. The Charlotte Belt is composed of Precambrian and Paleozoic bedrock, which
is dominantly plutonic with plutons ranging from granite to gabbro. The oldest rocks in the
Charlotte Belt are mafic gneisses, amphibolites, metagabbros and metavolcanic rocks, with
lesser amounts of biotite gneiss, granitic gneiss, mica schist, quartzite, and ultramafic rocks.
Mica schists and mica hornblende gneisses locally have been intruded by granite. The bedrock
underlying the facility consist of mostly diorite, gabbro, and granite. The predominate strike of
metamorphic rock foliation in the immediate area is to the northeast and northwest with dips
ranging from 70' to 80' to the northwest to vertical. The nearest fault to the proposed Phase V
expansion is a reverse fault approximately 11 miles to the northwest.
The bedrock in the Piedmont is typically overlain by a mantle of weathered rock or saprolite that
has an average thickness of approximately 25 feet. The saprolite consists of varying amounts of
unconsolidated clays, silts and sands, with lesser amounts of rock fragments. Due to the range
of the parent rock composition and the variable susceptibility to weathering of each rock type,
the saprolite ranges widely in color, texture, and thickness. Generally, the saprolite is thickest
near interstream divides (ridges) and thins toward stream beds. In profile, the saprolite normally
grades from clayey soils near the land surface to sandier partially weathered rock above the
competent bedrock.
Groundwater, beneath the facility, is present in the uppermost shallow, unconfined aquifer
comprised of unconsolidated soils and partially weathered, fractured, meta -volcanic rock.
Groundwater occurs at depths ranging from near ground surface, approximately 8 feet, in
valleys to more than 50 feet below grade on steep hills. Depth -to -water measurements obtained
4 - North Carolina. NCGS, 1985. Geologic Map of North Carolina. Scale1:500,000

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Hydrogeologic and Geotechnical Investigation
during the November 2021 and April 2022 observation events were used to prepare a
groundwater surface contour maps presented in Appendix B.
3.2.2 Local Geology - 15A NCAC 13B.1623(a)(1)&(4)&(13)
The soil onsite was classified based upon the Unified Soil Classification System (USCS). In
addition, Standard Penetration Test results were conducted to provide a general assessment of
the relative density or consistency of the soil encountered. Appendix E contains a description of
the soil encountered in each boring. Selected samples were further evaluated by performing
particle size analyses and Atterberg Limits testing to verify the visual classifications. A testing
summary and laboratory results are included in Appendix F.
Particle size analyses were used as the primary means to characterize the soil and give an
indicator of soil permeability. Sieve analyses were performed in accordance with ASTM D
422-17.
The percentage of soil particles passing a #200 (0.075mm) sieve determines whether the soil
would be considered a fine-grained soil, such as silt or clay (greater than 50 percent passing),
or a coarse -grained soil, such as sand or gravel (less than 50 percent passing). Generally, the
results ranged from 17.9 to 81.8 percent passing a #200 sieve, indicating a mixture of fine and
coarse -grained particles. The percentage of coarse -grained particles generally increased with
depth in borings advanced during this investigation.
The Atterberg Limit testing was performed in accordance with ASTM D 4318-17 and was used
to assess constructability of on -site soils. Most soil samples tested revealed varying degrees of
plasticity and primarily contained silty sands that would indicate soils are suitable for use as
structural fill. Moisture content of samples below the groundwater table were higher than
optimum for use as fill and would therefore require additional drying and rework during
construction.
The site soils generally consist of layered sands separated by fine-grained soils (clay or silt) and
were classified as sandy lean CLAYS (CL), fat CLAYS (CH), clayey SANDS (SC), elastic SILT
(MH), SILT (ML), silty SANDS (SM), and poorly graded SANDS (SP). The quantity of fine-
grained soils does not appear to be sufficient for use in base grade cell construction. Soils are
consistent with those underlying existing Phases of the landfill. Use of fine-grained soils for
future construction of landfill slopes or other than typical building construction should be
avoided. The attached permeability test results should also be considered when selecting soil
for capping or liner materials.
Currently, there is a 112,629.43 CY of soil within Phase V that can be used for landfill
construction and operations assuming a base grade elevation of 662 to 685 feet MSL as
depicted in the geologic cross -sections. In addition, soil from future phases could be made
available from the property
Based on the grain size and typical permeability of the soils within the Phase V area, the lean
clay (CL) soil could be used as a clay liner, but the permeability of the clay has not been

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Hydrogeologic and Geotechnical Investigation
validated by laboratory testing. The significant quantities of SAND (SP) within Phase V area
have the potential for use as drainage material, but most quantities observed are below the
groundwater table. Excavated SAND (SP) above the groundwater table should be tested for
acceptable porosity and permeability rates prior to use in order meet project specifications at the
time of construction.
Bedrock was encountered during the investigation. Competent bedrock is a slightly fractured
Quartz Diorite. This concurs with the 1985 State Geological Map of North Carolina, which
identifies the bedrock as an intrusive metamorphosed Gabbro and Diorite from the Permian
Period. The bedrock underlies the proposed waste area at depths ranging from 22 to 90 ft bgs
or 589 to 611 feet MSL, based on four observed contact points in the boring data for the area
(MW-27A, MW-29A, MW-30, and MW-34A). Overlying the observed bedrock are more
weathered rock units that can vary with depth due to the chemical weathering of the rock. Some
portions of the weathered rock can be more resistant to the chemical weathering due to varying
mineralogical matrixes resulting in isolated or disconnected material that could be described as
boulders. This may result in difficult excavation, but would not be considered competent
bedrock. This material ranges from 4 to 90 feet bgs. There should be a sufficient buffer of
unconsolidated material between the proposed waste cell liner system and the competent
bedrock interface.
3.2.3 Fault Areas
The most recently published information regarding the location of known faults, available from
the USGS interactive map of seismic activity website 5 was reviewed. The map indicates the
closest known fault is approximately 10 miles west of the facility. This map indicates that there
has been recorded Holocene fault movements within 7,500 feet of the proposed Phase V, but
not directly associated with the known fault location. This was also observed on the NCDEQ
Historic Earthquake Map 6. A summary of the three seismic events recorded closest to the
Phase V area is presented in Table 3-2.
Table 3-2: Holocene Fault Activity
Date
Magnitude
Depth (ft)
Latitude/Longitude
Distance from
Facility (ft)
05/13/2019 (09:17 UTC)'
2.1
2,625
35.765°N 80.571 °W
7,500
05/13/2019 (09:22 UTC) 2
1.7
42,126
35.773°N 80.561 °W
8,750
05/13/2019 (09:25 UTC) 3
1.8
14,436
35.786°N 80.560°W
13,750
1 — Source: M 2.1 - 5 km SSW of Cooleemee, North Carolina (usos.00v
2 — Source: M 1.7 - 4 km S of Cooleemee, North Carolina (usgs.gov)
3 — Source: M 1.8 - 2 km S of Cooleemee, North Carolina (usas.00v)
Refer to Appendix D for copies of the above -mentioned documents.
5 - https://www.usgs.gov/natural-hazards/earthquake-hazards/science/information-region-north-carolina
6 - https://ncdenr.maps.arcgis.com/apps/opsdashboard/index.html#/8e85c4cbca9e4e738b95be875fd2feae

Rowan County Landfill I Site Hydrogeologic Charaterization Report
Hydrogeologic and Geotechnical Investigation
3.2.4 Seismic Impact Zones
The proposed Phase V waste disposal cell is not located within a seismic impact zone, which is
defined as an area that has a 10% chance of receiving a horizontal acceleration of 0.10g
(gravitational pull) or more from an earthquake every 250 years. This is documented in the most
recent USGS online publication "Probabilistic Earthquake Acceleration of 2% within 50 Years for
the United States, 2014." An evaluation of 2% probability of exceedance in 50 years is
statistically equivalent to 10% probability of exceedance in 250 years. The proposed cell
location is within an area where the maximum horizontal acceleration is between 8%g to 10%g
(2% probability of exceedance in 50 years). Refer to Appendix D for a copy of the map. Such
horizontal movement is unlikely to compromise the structural integrity of the cell liner, leachate
pond, or piping. The existing facility has experienced no impact from recent seismic activity
identified in Section 3.2.3.
3.3 Water Table Information - 15A NCAC 136.1623(a)(7)/(8)/(9)
3.3.1 Groundwater Level Measurements - 15A NCAC 13B.1623(a)(7)(A)
After wells were installed, MLA Design Group Inc. survey personnel surveyed the top of well
casing and ground elevation for each well to the nearest 0.01 feet. Refer to Appendix C for top
of casing elevations and other information related to the construction of the wells.
HDR measured depth to groundwater and calculated groundwater elevations in individual wells
and piezometers during nine monthly gauging events conducted between November 2021 and
June 2022. Groundwater elevations are shown adjacent to individual wells on the Groundwater
Potentiometric Map in Appendix B.
Historically, the potentiometric surface in the area generally mimics the contours of the ground
surface. Primary groundwater flow direction is toward the southeast with minor localized flow
directions to the valley segmenting the site.
Localized flow directions may be impacted by the construction of Phase V, but the overall flow
direction is anticipated to remain consistent with the current direction.
3.3.2 Vertical Flow Components - 15A NCAC 13113.1623(a)(7)(A)&(8)
Monitoring wells MW-32 and MW-32A were installed to evaluate vertical flow within the
unconfined aquifer onsite. The variation in groundwater elevation between each two co -located
wells is likely attributed to the horizontal hydraulic gradient present over the site (roughly 0.007
to 0.257). The calculated vertical flow direction at these co -located wells is downward with a
vertical gradient of 0.069. The flow net generated for the site shows little to no vertical flow
across most of the site. Refer to Appendix B for flow nets developed for the site.
3.3.3 Seasonal and Temporal Factors - 15A NCAC 13113.1623(a)(7)(B)&(C)
The groundwater monitoring data for the facility was reviewed for fluctuation of groundwater
levels from November 2004 to May 2022. Water levels were found to fluctuate by 1.09 to 5.87
feet in the last 7 months for the piezometers and 1.79 to 4.21 in the existing monitoring network
10

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Hydrogeologic and Geotechnical Investigation
wells in the vicinity of Phase V. This observed variation is primarily the result of natural
infiltration of precipitation events. Appendix C contains a graphical representation of seasonal
water level trends for the existing piezometers and monitoring wells. Variations in water levels
will be monitored until one full year of data is collected (November 2022).
3.3.4 Hydraulic Conductivities - 15A NCAC 13B.1623(a)(8)
Horizontal hydraulic conductivity data of the onsite soils were collected on December 22, 2021.
In -situ permeability was measured by performing slug tests on selected wells. Static water
levels were measured in the wells. Falling head slug tests were performed by rapidly introducing
a stainless -steel slug into the well, which raised the level of water (head) in the well. The water
level was measured and timed at regular intervals as the water level dropped to reach the
original static level. Rising head slug tests were performed by rapidly removing the stainless -
steel slug and measuring water level change in the well.
The slug test data were analyzed using the Bouwer and Rice solution in Aqutesolv software.
This method was used since the upper aquifer onsite would be characterized as unconfined.
Conductivity based on slug testing ranged from 3.30 x 10-3 to 1.29 10-4 cm/sec (3.65 x 10-' to
9.35 ft/day). The arithmetic mean conductivity is 1.00 x 10-3 cm/sec. The geometric mean is 5.82
x 10-4 cm/sec. Constant head permeability tests performed on select material varied from 1.68 x
10-4 to 6.32 x 10-5 cm/s, which is consistent with the slug test data. The data tables and graphs
can be found in Appendix G.
3.4 Aquifer Description- 15A NCAC 13B.1623(a)(8)
3.4.1 General
The groundwater in Rowan County is generally 8 to 50 feet bgs and is situated in a media of
sandy clays to silty sands transitioning to weathered rock. Within the proposed Phase V waste
cell, groundwater was encountered from 7.61 to 36.73 feet bgs. Note that portions of the
proposed Phase V cell have been excavated for supply of borrow soil.
The groundwater flow velocity is estimated using the following equation:
V = k•i/n, where,
V = advective velocity, feet per day
k = hydraulic conductivity � 1.10 feet per day (geometric mean based on slug test
data)
i = hydraulic gradient 0.0061 to 0.0153 based onsite-specific observations
n = porosity of the soil 0.30 (assumed, based on material types observed in
borings)
The arithmetic mean for the advective groundwater horizontal flow velocity within the shallow,
unconsolidated aquifer is 5.71 x 10-2 ft/day. The geometric mean is 3.42 x 10-2 ft/day.
The groundwater horizontal velocity appears to be influenced by fracture flow within the slightly
fractured Quartz Diorite bedrock. Calculated advective flow velocity in MW-29A, which is
11

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Hydrogeologic and Geotechnical Investigation
screened in the bedrock, was 1.0 x 10-4 ft/day compared to the geometric mean of 3.42 x 10-2
ft/day in the overburden soil matrix of the shallow unconfined aquifer.
3.4.2 Recharge and Discharge Areas - 15A NCAC 13B.1623(a)(2)(B)&(13)(A)&(B)
Groundwater recharge to the shallow unconfined aquifer in the vicinity of Phase V consists of
two recharge pathways. The primary recharge pathway for the aquifer is the upper topographic
elevations to the north to northwest. The secondary pathway for proposed Phase V area
consists of infiltration across the site during precipitation events. Groundwater discharges along
the southeast portion of the site to an unnamed tributary of Second Creek. There are no active
dewatering operations within proposed Phase V or the facility.
Recharge and discharge areas are shown on the Groundwater Potentiometric Maps in
Appendix B.
3.4.3 Influence of Natural or Man -Made Actives - 15A NCAC 13B.1623(a)(7)(D)&(11)&(12)
The following natural and man-made activities may influence the static water levels within the
shallow aquifer in the proposed Phase V expansion area.
NATURAL ACTIVIES
The average monthly rainfall totals for the central piedmont, in North Carolina, from 1980-
Present range from 3.55 to 4.58 inches 7. The average groundwater level recorded from 1985-
Present in the area at USGS observation well NC-142 is 17.4 feet below ground surface (bgs)
(814.29 ft MSL) 8. The lowest recorded level is 23.33 ft bgs (808.36 ft MSL) and the highest level
is 10.69 ft bgs (821 ft MSL) (Appendix C). Seasonal precipitation/infiltration is the primary
natural process affecting water table levels at the site.
MAN-MADE ACTIVITIES
Man-made activities, such as construction of geo-synthetic liners, underdrain systems, or storm
water structures could affect the static groundwater levels in the shallow aquifer within the
proposed Phase V expansion area.
The installation of impermeable geosynthetic liners at the base grade of the proposed Phase V
expansion is anticipated to deprive the aquifer of normal groundwater recharge, which will result
in a gradual lowering of the water table within and immediately adjacent to the limits of the
proposed waste unit.
As discussed in Section 2.6 above, there is an existing French -drain underlying Phases III and
IV that runs northwest to southeast and discharges to the eastern unnamed tributary. This
underdrain system effectively lowers the natural static groundwater level to maintain the
necessary buffer from the landfill liner system.
- Based on NOAA climatological data for the Greenville -Spartanburg Area of the Piedmont from 1980-2022
8 - USGS Groundwater Watch: Site Number: 355359080331701 - DV-025 (NC-142) NR MOCKSVILLE, NC
(REGOLITH) https://groundwaterwatch.usgs.gov/AWLSites.asp?mt=g&S=355359080331701&ncd=awl\
12

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Water Quality Monitoring Plan
A previous receptor survey of the landfill property and the adjacent properties, performed by
Buxton Environmental, Inc., 2011, identified one water -supply well (Well 35) within 880 feet of
the investigation area 9. The impact of surrounding water -supply wells on the water table at the
proposed Phase V expansion appears negligible (if any), due to the proximity of the wells to the
site, the anticipated limited use of the wells, and anticipated unconfined aquifer conditions at the
site.
The construction of storm water control structures immediately adjacent to the proposed Phase
V expansion may result in localized hydraulic head increases during rainy periods. This creates
a localized recharge area contributing to an increase of static groundwater levels.
3.4.4 Maps and Diagrams 15A NCAC 13B.1623(a)(6)&(9)&(10)
GEOLOGICAL MAPS
The most current geologic map specific to the region was available from the USGS and the
North Carolina Geological Survey. A copy of the Geologic Map of North Carolina 1985 showing
the area of investigation, is included in Appendix D.
CROSS -SECTIONS - 15A NCAC 13B.1623(a)(6)
Refer to Appendix B for a Geologic Cross Section Map containing cross sections for the site.
This identifies the strata, depth to bedrock, and weathered/difficult excavation materials
previously discussed in Section 3.1 and 3.2.2. The proposed boundaries for Phase V has been
delineated along with other construction features.
POTENTIOMETRIC MAPS AND FLOW NETS - 15A NCAC 13B.1623(a)(9)&(10)
Refer to Appendix B for a groundwater potentiometric plan for the site.
4 Water Quality Monitoring Plan- 15A NCAC 13B.1623(b)(3)
The water quality monitoring plan (WQMP) has been developed for the Phase V expansion and
has been included in August 2022 Construction Permit Application for Phase V. Note that
WSP/Golder and Associates have historically developed and implemented the WQMP for this
MSW landfill; HDR chose locations and installed monitoring wells that will become compliance
wells under the WQMP, but did not derive the overall groundwater monitoring program,
sampling methodology, or statistical methods included in the WQMP.
5 References
American Society for Testing and Materials. Standard Test Methods for Liquid Limit, Plastic
Limit, and Plasticity Index of Soils. ASTM D4318-17e1 (2017).
9 - Buxton Environmental, Inc., Design Hydrogeologic Report Revised Proposed Phase IV Subtitle D Municipal Solid
Waste Landfill Expansion Rowan County Landfill, January 2013.
13

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
References
American Society for Testing and Materials. Standard Test Method for Particle -Size Analysis of
Soils. ASTM D422-63(2007)e2.
Domenico, Patrick & Franklin Schwartz, Physical and Chemical Hydrogeology, John Wiley &
Sons. 1990
Freeze, Allen & John Cherry, Groundwater, Prentice -Hall, Inc. 1979
North Carolina. NCGS, 1985. Geologic Map of North Carolina. Scale1:500,000
Terzaghi, Karl & Ralph B. Peck, Soil Mechanics in Engineering Practice, John Wiley. 1962.
United States. Department of the Interior — Geological Survey. Basic Ground -Water Hydrology.
Water -Supply Paper 2220. 1998.
United States. Department of the Interior — Geological Survey. Seismic -Hazard Maps for the
Conterminous United States. Publication 3325. Mark D. Petersen et al. 2014.
United States. Department of the Interior — Geological Survey. Probabilistic Earthquake
Acceleration of 2% within 50 Years for the United States. 2014
United States. Department of Minerals and Mines. Geologic Map of North Carolina. 1985
14

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Appendix A - Maps
Appendix A - Maps
Site Vicinity Map
Aerial Map

Rowan County Landfill I Site Hydrogeologic Charaterization Report ���
Appendix A - Maps
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MANHOLE
HDR Engineering, Inc.
440 South Church Street, Suite 1200
Charlotte, NC 28202
704.338.6700
PROJECT MANAGER P. WESTMORELAND, PE
PROJECT ENGINEER
P. WESTMORELAND, PE
GEOLOGY D
A. WHITE, P.G.
A 04/2022 ISSUED FOR APPROVAL
DRAWN BY
T. PREDDY, E.I.
ISSUE DATE DESCRIPTION
PROJECT NUMBER
10314393
OWA,y
ROWAN COUNTY LANDFILL
Salisbury
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PHASE V
HYDROGEOLOGIC REPORT
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