NC0004961_RBSS CSA Report_Appendix C_Source Characterization_20150818

Drilling Procedures
Drilling Techniques
In general, deep borings were advanced using 4'/4 inch inner diameter (ID) hollow stem augers
(HSAs) to create a pilot hole for the larger 7 7/8 inch tri-cone mud rotary bit and collect
environmental/geotechnical samples. Once refusal was encountered using the smaller ID HSAs,
then a 7 7/8 inch tri-cone was advanced to one to two feet below refusal (when feasible) to
install the 6 inch PVC outer casing (details provided in Well Installation Procedures below).
Once grout was allowed to cure for approximately 24 hours, HQ coring tools were utilized to
advance the borehole at least 15 feet below bottom of outer casing. Borehole was then reamed
with a 4 or 5 inch diameter roller or tri-cone bit to allow for 2 inch diameter monitoring well
installation.
Bedrock borings were installed using same drilling techniques as detailed above except the
borehole was advanced 50 ft below the bottom of the outer casing. In select locations where
bedrock borings were paired with deep borings, wells were double cased (telescoped) to
eliminate potential mixing of zone being monitored in the deep boring and zone being monitored
in the bedrock boring. To simplify, a 6 in outer casing was installed as mentioned above to
bedrock, then boring was advanced 15 to 16 ft below outer casing using a 5 7/8 roller or tri-cone
bit to set a 5 in outer casing. Once grout was allowed to cure for approximately 24 hrs the boring
was advanced 50 ft below the bottom of the 5 in outer casing. Boring was then reamed using a
4 in diameter roller or tri-cone bit as described above and monitoring well installed.
Shallow borings were advance using 4 % in ID HSAs to a termination depth based on
observations made during advancement of the deep boring and monitoring well was installed.
Monitoring well installation is described in greater detail in the Well Installation Procedures.
In addition to HSAs, mud rotary and coring techniques, the use of sonic drilling was utilized to
augment conventional drilling techniques. For deep and bedrock well installation, a 6 inch
sampler was advanced in 5 to 10-foot sections to gather subsurface material to refusal. A 10
inch recovery bit was advanced to the same depth as the 6 inch bit and advanced and
additional 1 to 2 feet to set an outer 6-inch PVC casing. Once grout was allowed to cure for
approximately 24 hours, the boring was completed with HQ core tooling as described in the
Deep and Bedrock Monitoring Well Installation Procedures.
In some cases, shallow wells were installed using sonic drilling technology. The procedure for
shallow well installation is similar to the deep and bedrock well installation technique; however,
due to the absence of 6 inch outer casing in these wells, a 4 inch sampler and a 6 inch recovery
bit were utilized. Well completion procedures for shallow wells are detailed in the following
section.

Shallow Monitoring Well Installation Procedures
Shallow monitoring wells were installed to monitor the regolith zone or ash and are identified
with an "S" (shallow) or "SL" (shallow lower) qualifier in the well nomenclature. If the regolith
zone was observed to be relatively thick or more than one water bearing zone was encountered
during drilling, a second shallow monitoring well was installed to monitor the lower water bearing
zone and was identified as the SL well. Shallow monitoring wells were installed at the Site using
either hollow stem auger (HSA) or mud rotary (roller or tri-cone bit) drilling techniques. Shallow
monitoring wells were installed to monitor regolith aquifer or if installed in a dam, wells were
installed to monitor the phreatic surface within the ash basin(s). Each shallow well was
constructed with ten feet (ft) to fifteen ft of two inch diameter schedule 40 PVC 0.012-inch
slotted pre -packed screen and schedule 40 PVC riser to grade or above grade if needed. A #2
filter pack sand was placed one to two feet above the pre -packed screen, bentonite was placed
one to two feet above the sand pack, and borehole was completed to grade with grout via
positive displacement method (tremmie grouting). If the boring was in an access path or
roadway the well was completed at the surface with a flush mount well cover and locking well
cap. If the boring was located off access paths and roadways the well was completed at the
surface with a four inch above grade protective casing with lock and bollards to protect the
monitoring well.
Deep Monitoring Well Installation Procedures
Deep monitoring wells were installed to monitor the transition zone (if present) and are identified
with a "D" (deep) qualifier in the well nomenclature. Deep monitoring wells were installed using
HAS, mud rotary or sonic drilling techniques to approximately one to two feet below refusal
where a six inch diameter schedule 40 PVC outer casing was installed to seal off the
overburden. Grout utilized for outer casing installation was allowed to cure for twenty-four hours
then boring was advanced approximately fifteen feet below the bottom of the outer casing using
HQ coring tools. Rock cores were logged in accordance with the Field Guide for Rock Core
Logging and Fracture Analysis by Midwest GeoSciences Group and cores were photographed.
Each deep well was constructed with five ft of two inch diameter schedule 40 PVC 0.012-inch
slotted pre -packed screen and schedule 40 PVC riser to grade or above grade if needed. A #2
filter pack sand was placed one to two feet above the pre -packed screen, bentonite was placed
one to two feet above the sand pack, and borehole was completed to grade with grout via
tremmie grouting method. If the boring was in an access path or roadway the well was
completed at the surface with a flush mount well cover and locking well cap. If the boring was
located off access paths and roadways the well was completed at the surface with a four inch
above grade protective casing with lock and bollards to protect the monitoring well.
Bedrock Monitoring Well Installation Procedures
Bedrock monitoring wells were installed to monitor fractured bedrock and are identified with a
"BR" qualifier in the well nomenclature. These wells are screened across water bearing
fractures within competent bedrock. Bedrock monitoring wells were installed using either HAS,
mud rotary or sonic drilling techniques to approximately one to two feet below refusal where a

six inch diameter schedule 40 PVC outer casing was installed to seal off the overburden. Grout
utilized for outer casing installation was allowed to cure for twenty-four hours then boring was
advanced approximately fifty feet below the bottom of the outer casing using HQ coring tools.
Rock cores were logged in accordance with the Field Guide for Rock Core Logging and
Fracture Analysis by Midwest GeoSciences Group and cores were photographed. Packer
testing was performed on select fractures observed in the rock cores. Screen interval was
selected based on observations made during coring activities and packer test results. Each
bedrock well was constructed with five ft of two inch diameter schedule 40 PVC 0.012-inch
slotted pre -packed screen and schedule 40 PVC riser to grade or above grade if needed. A #2
filter pack sand was placed one to two feet above the pre -packed screen, bentonite was placed
one to two feet above the sand pack, and borehole was completed to grade with grout via
tremmie grouting method. If the boring was in an access path or roadway the well was
completed at the surface with a flush mount well cover and locking well cap. If the boring was
located off access paths and roadways the well was completed at the surface with a four inch
above grade protective casing with lock and bollards to protect the monitoring well.
Soil Sampling Procedures
For nested monitoring wells, the deep boring was utilized for characterization of subsurface
material and collection of environmental and/or geotechnical samples for lab analyses. Standard
Penetration Testing (SPT) was conducted utilizing split -spoon sampling techniques at five foot
increments with an 18-inch split -spoon sampler. Any environmental and/or geotechnical
samples not able to be collected in the deep well were collected in either the shallow or bedrock
well that was paired with the deep well. Geotechnical samples consisted of undisturbed (Shelby
tube) samples (natural moisture content, grain size with hydrometer, hydraulic conductivity, and
specific gravity), sorption samples (Kd/HFO), mineralogy, and index property samples (natural
moisture content and grain size with hydrometer). Environmental sampling for soils consisted of
Total Inorganic compounds (TI) and Total Organic Carbon (TOC) and environmental sampling
for ash consisted of TI, TOC, and Synthetic Precipitation Leaching Potential (SPLP). In
situations where there was a single well to installed, as many samples as possible were
collected in that boring, but if it was not feasible to collect the necessary samples a second
boring (geotechnical boring) was advanced within five ft of the original boring to obtain the
remaining samples.
Sampling equipment was decontaminated between each sample interval in the same borehole
as well as between each boring. Sampling equipment was first rinsed with tap water, washed
with a water-liquinox mix and then rinsed a final time with deionized water. All downhole
equipment utilized during boring/well installation (i.e.; augers, drill rods, split spoons, etc.) were
decontaminated between each borehole to eliminate potential cross contamination between
boreholes. A decontamination pad was constructed for field cleaning of downhole tooling.
Downhole tooling was decontaminated using a high temperature, high pressure steam cleaner
followed by rinsing with potable water.

Hydrogeologic Evaluation Testing
To better characterize hydrogeologic conditions, falling and constant head tests, packer tests,
and slug tests were performed. Data collected from these tests will be used in the groundwater
modeling.
At select deep/bedrock well locations, horizontal permeability tests (falling or constant head
tests) were performed just below refusal in the upper bedrock (transition zone if present). At
select shallow/deep/bedrock locations, vertical and horizontal permeability tests were conducted
above refusal in varying hydrostratigraphic units.
Packer testing was conducted in bedrock borings at select fractures based on observations
made during drilling and the rock cores. In general, a double packer system was utilized with
generally five to teen feet of separation between packers and a single packer system was
utilized to perform a shut in permeability test at the bottom of the borehole.
Slug tests were completed in each monitoring well installed to assess hydraulic conductivity.
Slug tests were conducted in accordance with requirements of the NCDENR Memorandum
titled, "Performance and Analysis of Aquifer Slug Tests and Pumping Tests Policy", dated May
31, 2007.

Drilling and Installation Variances

AS-2D
1
2 AS-3S
3
4
5
6
7
8
9
10
11
12
Variances from Groundwater Assessment Work Plan
AB-5S/D original location
AB-7S/D original location
AB-8S/D original location
C-1 S/D original location
C-1 D
C-2S/D original location
AB-7SL
GWA-2D
GWA-3S
Source Characterization
AS-21D, AS-2D-A, and AS-2GT
AS-3S-A near existing well cluster
AS-3
AB-5S/D location moved
approximately 600 ft south-southeast
AB-7S/D location moved
approximately 200 ft southeast
AB-8S/D location moved
approximately 100 feet north-
northwest
C-1 S/D location moved
approximately 250 feet northeast
C-1 BRU
C-2S/D location moved
approximately 200 feet east-
southeast
AB-71
GWA-2BRU
GWA-3S-A
Well AS-2D-A (original hole) had tooling stuck in
hole; AS-21D was drilled to a lower depth of rock,
leading to AS-2GT for additional sampling
Well could not be developed, and a replacement
well was needed
New location is on more stable ash for safer drilling
No transition zone was present; name was changed
to bedrock upper (BRU)
New location is on more stable ash for safer drilling
New location is away from the rail line, transmission
line, and ash sluice lines for long-term access and
safer drilling
New location is better located for long-term access,
more cinder material, and safer access.
No transition zone was present; name was changed
to bedrock upper (BRU)
New location is better for safety while drilling
Due to the shallow depth of ash at this location, the
SL well was not installed due to overlapping with the
depth of the S well. An intermediate (1) well was
installed in the soil/saprolite layer below the ash and
_above the partially weathered rock.
No transition zone was present; name was changed
to bedrock upper BRU
Well GWAS-3S was dry, could not be developed,
and a replacement well was needed

s Proposed
13
14 I GWA-9S/D/BR original location
GWA-9BR
15
16 GWA-1OD
17 None
18
19
20
21
22
23
GWA-7BR-A
GWA-9S/D/BR location moved
approximately 200 ft south
GWA-9BR-A
GWA-10BRU
GWA-20S/D/BR
None GWA-21 S/D/BR
None GWA-22S/D/BR
GWA-22BR GWA-22BR-A
Core barrel broke while in the hole and was not
retrieved. GWA-7BR was grouted; GWA-7BR-A
was offset and drilled as a replacement
New location is outside of the wetlands and FERC
boundaries.
Core barrel broke while in the hole and was not
retrieved. GWA-9BR was grouted; GWA-9BR-A
was offset and drilled as a replacement
No transition zone was present; name was changed
to bedrock upper (BRU)
The proposed wells were added to provide
additional information in the area around MW-8S/I/D
The proposed wells were added to provide
additional information in the area around MW-
8S/I/D; GWA-21 S/D have been installed as of the
issuance of this report and GWA-21 BR is in process
The proposed wells were added to provide
additional information in the area around MW-8S/I/D
Core barrel broke while in the hole and was not
retrieved. GWA-22BR was grouted; GWA-22BR-A
was offset and drilled as a replacement
None GWA-23S/D/BR The proposed wells were added to provide
additional information in the area around MW-8S/I/D
None MW-9D/BR NCDENR requested monitoring wells 200 feet north
of the existing monitoring well MW-9 to screen
various flow paths but the surrounding wetlands
limited the location to the same proximity as MW-9
None MW-15D/BR NCDENR requested additional monitoring wells
near the existing monitoring well MW-15 to screen
various flow paths