NC0003468_DRSS CSA Rpt_Appx D_Soil and Rock Characterization_20150814

Appendix D
Soil and Rock Characterization
• Sampling Procedures
• Sampling Variances

Sampling Procedures
Sampling Overview
Characterization of subsurface materials was conducted through the completion of soil borings
and borings performed for installation of monitoring wells as shown in Section 6. Installation
details for soil borings and monitoring wells, as well as estimated sample quantities and depths,
are described below.
For nested monitoring wells, the deep monitoring well boring was utilized for characterization of
subsurface materials and collection of samples for laboratory analysis. Shallow, deep, and
bedrock monitoring well borings were logged in the field as described below.
At the conclusion of well installation activities, well construction details including casing depth;
total well depth; and well screen length, slot size, and placement within specific
hydrostratigraphic units were presented in tabular form for inclusion into the final CSA Report.
Well completion records were submitted to NCDENR within 30 days of completion.
Duke Energy acknowledges that subsurface geophysics may be useful for evaluation of
subsurface conditions in areas of the site that have not been significantly reworked by
construction or ash management activities, but less useful in basins and fills. Subsequent to
evaluation of field data obtained during the proposed investigation activities, Duke Energy
evaluated the need for and potential usefulness of subsurface geophysics in select areas of the
site. If it was determined that subsurface investigation was warranted, Duke Energy and HDR
notified the NCDENR regional office prior to initiating additional investigations.
Ash and Soil Borings
Characterization of ash and underlying soil was accomplished through the completion and
sampling of borings advanced at 9 monitoring well locations within the active ash basin and on
the north and east dikes (designated as AB-20 through AB-28), 11 monitoring well locations
within the inactive ash basin and on the east dike (designated as AB-29 through AB-39), 6 soil
boring locations in the west portion of the inactive ash basin (designated as SB-1 through SB-6),
and 3 soil boring locations in the active ash basin area (SB-7 through SB-9). In addition, 12 soil
borings (designated as GWA-1 through GWA-9 and BG-1 through BG-3) were completed
outside of ash management areas to provide additional soil quality data.
Note that Duke Energy notified the Division of Waste Management (DWM) prior to installing
proposed borings/monitoring wells located adjacent to the RAB Ash Landfill (designated as
AB-29S/D through AB-34S/D) and within and adjacent to the structural fill area (designated as
SB-4, SB-5, SB-6, AB-35S/D/BR, and AB-39S/D). No borings were advanced within the
footprint of the double-lined ash landfill located in the east portion of the inactive ash basin.
Field data collected during boring advancement was used to evaluate:
• the presence or absence of ash
• areal extent and depth/thickness of ash
• groundwater flow and transport characteristics if groundwater was encountered

Borings were advanced using hollow stem auger or roller cone drilling techniques to facilitate
collection of down-hole data. Standard Penetration Testing (SPT) (ASTM D 1586) and split-
spoon sampling were performed at 5-foot increments using an 18-inch split-spoon sampler. Soil
borings located within the waste boundary that were not used for installation of monitoring wells
(SB-1 through SB-9) extended approximately 20 feet below the ash/native soil interface or to
refusal, whichever was encountered first. Note that continuous coring was performed from
auger refusal to a depth of at least 50 feet into competent bedrock for bedrock monitoring well
borings (designated as BR soil boring/groundwater monitoring well locations).
Borings were logged and ash/soil samples were photographed, described, and visually
classified in the field for origin, consistency/relative density, color, and soil type in accordance
with the Unified Soil Classification System (ASTM D2487/D2488).
Borings within Ash Basin Waste Boundary
In areas where ash was known or suspected to be present (i.e., AB- and S-borings), solid phase
samples were collected for laboratory analysis from the following intervals in each boring:
• Shallow Ash – approximately 3 feet to 5 feet bgs
• Deeper Ash – approximately 2 feet above the ash/soil interface
• Upper Soil – approximately 2 feet below the ash/soil interface
• Deeper Soil – approximately 8 feet to 10 feet below the ash/soil interface

If ash was observed to be greater than 30 feet thick, a third ash sample was collected from the
approximate mid-point depth between the shallow and deeper samples. The ash samples were
used to evaluate geochemical variations in ash located in the ash basin and ash storage. The
upper and deeper soil samples were used to delineate the vertical extent of potential soil
impacts beneath the ash basin and ash storage.
Ash and soil samples were analyzed for total inorganic compounds.
Select ash samples were analyzed for leachable inorganic compounds using the Synthetic
Precipitation Leaching Procedure (SPLP) to evaluate the potential for leaching of constituents
from ash into underlying soil. The ash SPLP analytical results were compared to Class GA
Standards as found in 15A NCAC 02L .0202 Groundwater Quality Standards, last amended on
April 1, 2013 (2L Standards).
Ash was located at varying depths beneath the ponded water areas within the active ash basin.
Due to safety concerns, borings were not completed where ponded water was present within
the ash basin. Safety concerns may also prevent access to proposed boring locations on ash
areas where saturated ash presents stability issues.
Borings Outside Ash Basin Waste Boundary
Borings located outside the ash basin waste boundary were designated as GWA and BG
borings.
The GWA soil samples were used to provide additional characterization of soil conditions
outside the ash basin boundary. Solid phase samples were collected for laboratory analysis
from the following intervals in each boring:
• Approximately 2 feet to 3 feet above the water table
• Approximately 2 feet to 3 feet below the water table
• Within the saturated upper transition zone material (if not already included in the two
sample intervals above)
• From a primary, open, stained fracture within fresh bedrock if existent (bedrock core
locations only)

The boring locations designated as BG borings were used to evaluate site-specific background
soil quality. Solid phase samples were collected for laboratory analysis from the following
intervals in each boring:
• At approximately 10-foot intervals until reaching the water table (i.e., 0 feet to 2 feet, 10
feet to 12 feet, 20 feet to 22 feet, and so forth)
• Approximately 2 feet to 3 feet above the water table
• Approximately 2 feet to 3 feet below the water table
• Within the saturated upper transition zone material (if not already included in the two
sample intervals above)
• From a primary, open, stained fracture within fresh bedrock if existent (bedrock core
locations only)

The laboratory analyses performed on the GWA and BG samples depended on the nature and
quantity of material collected.
One or more of the above listed sampling intervals may be combined if field conditions indicate
they were in close proximity to each other (i.e., one sample was obtained that was applicable to
more than one interval).
Index Property Sampling and Analyses
In addition, physical properties of ash and soil were tested in the laboratory to provide data for
use in groundwater modeling. Split-spoon samples were collected at selected locations with the
number of samples collected from the material types as follows:
• Fill - 5 samples
• Ash - 5 samples
• Alluvium - 5 samples
• Soil/Saprolite - 5 samples
• Soil/Saprolite - immediately above refusal - 5 samples
Select split-spoon samples were tested for:
• Natural Moisture Content Determination in accordance with ASTM D-2216
• Grain size with hydrometer determination in accordance with ASTM Standard D-422
The select split-spoon samples were anticipated to be collected from the following boring
locations:
• Fill – AB-22S/D, AB-26S/D, AB-28S/D, AB-31S/D, and AB-32S/D
• Ash – AB-21S/D, AB-25S/D, AB-29S/D, AB-34S/D, AB-37S/D, and SB-3
• Alluvium (if present) – GWA-3S/D (2 samples), GWA-4S/D, and GWA-5S/D (2 samples)
• Soil/Saprolite (two locations each as stated above) – BG-2S/D/BR, GWA-1S/D,
GWA-3S/D, GWA-6S/D, and AB-35S/D/BR

The depth intervals of the select split-spoon samples were determined in the field by the Lead
Geologist/Engineer.
In addition to split-spoon sampling, a minimum of five thin-walled undisturbed tubes (“Shelby”
Tubes) in fill, ash, and soil/saprolite layers were collected from the above-referenced boring
locations. Sample depths were determined in the field based on conditions encountered during
borehole advancement. The Shelby Tubes were transported to a soil testing laboratory and
each tube was tested for the following:
• Natural Moisture Content Determination in accordance with ASTM D-2216
• Grain size with hydrometer determination in accordance with ASTM Standard D-422
• Hydraulic Conductivity Determination in accordance with ASTM Standard D-5084
• Specific Gravity of Soils in accordance with ASTM Standard D-854

The results of the laboratory soil and ash property determination were used to determine
additional soil properties such as porosity, transmissivity, and specific storativity. The results
from these tests were used in the groundwater fate and transport modeling. The specific borings
where these samples were collected from were determined based on field conditions with
consideration given to their location relative to use in the groundwater model.

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